I have the same tic. It drives my boss crazy. I loathe the New York Times for this. Very frustrating! I also tend to draw squares with my mouse on my desktop. I don't know why.
(As for Adblock, I don't mind some non-invasive adverstising, but moving graphics and the like completely distract me. The only way I can use a site is to get such out of view.)
P.S. Adblock Plus, actually.
P.P.S. I'd been removing distracting items from page views on a case by case basis (attempt to use page; remove anything thereupon overly distracting me, on a one time basis using another Firefox extension). I no longer recall for certain, but it may have been the NYT's new behavior that finally tipped the balance and brought me to try Adblock Plus. As I think back on it, an interesting, if anecdotal, reflection on the perhaps unexpected incentive effects of site design.