evath has, I notice, committed the blunder so many do when pointlessly trying to avoid prepositions at the end of clauses and sentences. She says: "as in that last bit, which is an example of which we are speaking," which makes no grammatical sense, nor is it idiomatic. The natural way to write it would be: "as in that last bit, which is an example of what we are speaking of (or about)" In trying to shift that "of" from the end, evath has missed it out altogether. I imagine he/she meant to write: "as in that last bit, which is an example of that of which we are speaking." I would hardly call that elegant.

Why don't people check their facts before spouting such drivel? The simplest Google books search shows that all three forms have been in use since at least the 19th century. M-WDEU records all three, too. The OED gives not only by, with and of but on and upon - with examples going back to the 14th century. These are all verifiable facts of usage, rather than the misinformed opinions of someone who insists on using 'devolve' in a sense that the OED describes as obsolete.