Just in case anyone missed the recent Language Log post, here is my definition of a the new verb.
anniversary v. tr. 1. To make an annual event.
We had so much fun at our spontaneous golf outing with friends that we decided to anniversary it.
I think that Geoffrey K. Pullum hit the nail on the head with his take on the oddity of this particular verbing.
"I don't mean to suggest that there's anything particularly wrong with verbing new nouns, of course: you can pretty much verb any noun you want to verb. But if you pick a solidly nouny noun and use it without warning or precedent as a verb, it may cause a certain shock, and the people who say "Whoa, wait a minute!" are not wrong to object: you are stepping right outside the bounds of their linguistic experience, and you can't expect them to pretend that isn't so."