I never noticed impact being used as a verb until news reporters and other television announcers of that ilk began using it that way. There is, apparently, no "style" book for their trade and, though they often refer to themselves as journalists, they habitually reveal ignorance of proper English grammar and usage in this way.
In fact, I sent an email to a local news station about this very thing and was told in the reply that he (the writer) knew it was wrong, but that he allowed it because "English is a dynamic language."
Enough wrongs, in other words, make a right.