http://factor1.net/main/index.html
Hover over my "This is a tool tip" on the right, and lower left.
It is real easy to do, but I have seen some much more intrusive and persistant crap like this with flash and with a 'small' banner for "Windows 2003 Server" on the pcmag site. On mouseOver, a 400 x 70 sized banner in the header would suddenly expand to occupy the whole viewport at 1024 res, well, all the text I was trying to read anyways - it didn't cover up any other ads.
I am starting to get very annoyed with all the advertising on pcmag, globe and mail, and other 'respectable' sites that make reading the articles almost impossible, and I wouldn't doubt it if they could induce siezures LOL.
These sites, 'computerworld' here as well, download copious amounts of tracking cookies from "Avenue A Inc." and "MediaPlex" surriptitiously - at the rate of two per page visited.
I think we are going through a renaissance of web advertising, and who knows the depths of depravity we will sink to in our quest for the blessing of the almighty God "Moolah".