@jayles - I would say all three are valid sentences, but not all necessarily valid extrapolations from your original sentence.

I agree with you that B is an adjective and not a passive. And you're right that A is intransitive, because pile up is a so-called ergative verb such as, for example, cooking verbs or verbs like 'break'. These can be used in three ways: transitively, intransitively with the object of the transitive verb becoming the subject of the intransitive verb, and in the passive -

She was boiling some eggs for supper.
The eggs were boiling nicely
The eggs had been boiled for exactly four minutes

We can do the same with 'pile up', especially in its literal sense:

The wind had piled up the leaves in the corner of the yard
The leaves had piled up in the corner of the yard
The leaves had been piled up in the corner of the yard by the wind.

http://random-idea-english.blogspot.com/2011/08/ergative-verbs-what-on-earth-are-they.html

In your sense of pile up, however, we are probably less likely to use it transitively (and you didn't in fact give an active transitive example), as we tend to think it's something that has happened outside our control - either of its own accord, as suggested in A, or by forces unknown, as in B. Unless of course we know that someone else has piled it up, which is where C comes in.

And although I agree with Jasper that they're practically the same thing, I find A stronger, as it suggests that the work has a will of its own, whereas the adjective version (B) is more neutral.

But to get a bit pernickety, I don't think we can extrapolate Sentence A from your original sentence - "She stared at the work piled up on the desk.". For me, this involves a reduced relative clause, which could be read two ways - "She stared at the work (that/which was) piled up on the desk" - linking verb 'be' + adjective 'piled up' (B), or "She stared at the work (that/which had been) piled up on the desk" where 'had been piled up' is a passive (C).

To make reduced relative clauses from active verbs, on the other hand, we only use a present participle - "She looked at the work piling up in front of her eyes", and not usually for completed events.

So, while A is a perfectly valid sentence, I don't think you can reduce "She stared at.the work that had piled up on the desk" to "She stared at.the work piled up on the desk" without changing the meaning away from the active intransitive to a passive or adjectival construction.

If we say "He looked admiringly at the flowers that had grown in such poor soil" (active intransitive) it suggests that his admiration is directed at the flowers, which had managed it all by themselves. But if we say "He looked admiringly at the flowers grown in such poor soil", it suggests to me that his admiration is directed more at the person who grew them; for what we have here is a passive transitive construction.

@Thredder - Mais ca, c'est pas logique! Pour une personne on a besoin d'au moins deux oeufs, n'est-ce pas? Sorry, but I don't follow your logic. Or am I missing something?

@Hairy Scot - I thought you'd gone AWOL! Care to explain (in a language context)?

@Brus - ROFLMAO = Rolling on the floor laughing my ass off - not so much hare-speak as web-speak. No, I didn't know either, but I do have Google. I think we can imagine what the extra S and F might be. Incidentally, hares don't live in burrows but in 'forms', depressions of flattened grass.

@jayles - I'm certainly not defending business speak. As for PC language, my dictionary defines 'politically correct' as - 'used to describe language or behaviour that deliberately tries to avoid offending particular groups of people'. Nothing wrong with that, but it now seems to be mainly used as a derogatory term, especially by those on the political right. But just remember, every time you call somebody 'gay' and not 'homosexual' or 'Chinese' rather than 'a Chink', you are in fact using PC language.

But neither of these is to do with snobbery. And I find something slightly distasteful about labeling a whole group of individuals as 'middle management', whose motives and aspirations Brus is apparently privy to. Many of my students are 'middle management', and perfectly decent people with families and with aspirations pretty similar to the rest of us.

All they are really doing is using the language of their peer group, just like other peer groups such as teenagers, a lot of which they no doubt pick up at MBA courses or from 'motivational' books and training courses. Some of them may indeed want to sound smart and 'on the ball', but I doubt that this has much to do with trying 'to convey the impression they mix in circles where such business-speak is all the rage'.

between seeing visions, they employ such terms to try to convey the impression they mix in circles where such business-speak is all the rage. Middle management, in other words. That is their aspiration. Being 'on the ball'..

@Brus - I'm not calling you a snob, but I don't think you realise how these expressions used to be used by the many people who took the the whole thing quite seriously, even while joking about it.

@Brus - I was brought up on all this U and Non-U stuff and it's just pure snobbery. And sorry, but the very act of calling somebody non-U is also one of snobbery. I know, because I used to think that way myself when I was a young public-school boy who didn't know any better. To call somebody non-U was not a neutral sociological observation, but a social put-down.

Being U has nothing to do with 'correct' language or not speaking business speak, simply of going to the 'right' schools, using the 'right' words, wearing the 'right' clothes and holding your knife a certain way. Fortunately, since the sixties, Britain has been taking steps to rid itself of some of this sort of class nonsense, and things like the adoption of Estuary English or even Mockney by some members of the upper-middle classes are in some way a reaction to it. Innit, mate?

http://en.wikipedia.org/wiki/U_and_non-U_English

@Brus - We've already talked about Nancy Mitford and the whole idea of 'U and Non-U' on another thread, but I'm not sure what calling a serviette a napkin, or the toilet the lavatory (or the loo, or possibly the bog; anything except toilet), and not saying anything perceived to be 'common' has to do with verbing. She may have meant it as a joke, but it became a sort of snobbish code - 'Anyone who says "lounge", darling, simply can't be "people like us". '

@Brus - Actually, I wrote a blog post about this a couple of years ago, where I warn foreign learners about possible reactions to using business buzzwords, although in a fairly light-hearted way. - http://random-idea-english.blogspot.com/2010/10/loop-back-to-me-and-well-touch-base.html

@Brus - I have some sympathy with your views on business speak, witness the question I posted about 'reach out to' meaning to contact (do you include the verb 'contact' in this 'abominable violence perpetrated upon the English language', by the way?). As for Obama, excellent speaker though he is, he is rather prone to use the expression 'going forward', which I'm afraid is more business speak, one which Lucy Kellerman at the FT tried to put a stop to, but failed. Here are a couple of websites I think you might like:

http://www.johnsmurf.com/jargon.htm
http://www.theofficelife.com/business-jargon-dictionary-L.html

I quite agree that some of these expressions, like 'decisioning something' are daft, and a recent report has shown that the use of such language pisses employees off no end. But you don't really address my point that this verbing or verbification has been going on for centuries, it's just the fact that the revolution in communications has made it much easier for newly-coined ones to be circulated and it's usually only the more recent ones that rankle - I notice you were fairly selective in the examples of mine that you mentioned - nothing about salt, pepper, ship or parts of the body. And 'impact', which seems to annoy a lot of people, was in fact a verb before it was a noun.

There are lots of words and expressions I don't particularly like, but let's get things in perspective - nobody is perpetrating any violence on anything; I would have thought that such a stickler for language as you would choose his words a little more carefully. People have been playing with the language and creating new words no doubt since the dawn of language. Some stay, some fall by the wayside. There's a good, relatively neutral, article at the Economist:

http://moreintelligentlife.com/content/ideas/anthony-gardner/youve-been-verbed