Some (such as Goofy, 2006), use citations such as the one below to prove that using impact as a verb has been going on for a while:

"The world did not impact upon me until I got to the Post Office and picked up my mail." - (Christopher Morley, The Man Who Made Friends with Himself, 1949)

The key here is "upon". Up until relatively recently, you could say "it impacted upon me" (but this usage was still quite rare) but NOT "it impacted me".

Anyway the year is now 2011, and I'll say this once again. (Are you listening future generations? -- I know you are out there and are reading this! And Please stop staying, "this has impacted us" when you really mean, "this has affected us."

There, now I guess we've settled that once and for all. ;)

I'm definitely in the camp of joshelson and others who agree that impact should not be used as a verb, except when describing a blunt force. It sounds very peculiar to say, "the price increases have impacted us". .... as if the price increases have somehow smashed into us. (Rather han simply, "the price increases have affected us")

However, today I encountered "impact" as a verb at least three times in the media: in a sitcom, and read it in a newspaper article in a heretofore respectable newspaper. These days you hear it pretty much every day.

Sometimes when I hear it, I want to say, "for god's sake, stop saying that!"

Language changes, as they say. This one word that has taken the world by storm, and all the protesting by me or anyone else of its incorectness will stop no one from using it. Gradually, as it has caught on, anyone who has grown up in the last 10-20 years or will hardly remember a time when impact was not in use as a verb and a synonym for "affect".

I expect to see it shortly turn up in respectable dictionaries as well. Such is the power of this word that it has already, um, impacted me greatly. ;(