I've come across two sites today (oddly, both were blogs hosted on blogger) , that have a somewhat annoying Snap.com popup over links, that gives you a preview of what the link looks like. Of course, there's no direct way of turning this off (fortunately, Adblock comes to the rescue - adding http://spa.snap.com/snap_preview_anywhere* as a filter gets rid of it).
If I wanted such functionality, I'd already be using Cooliris (which I have installed and do use when I want that functionality - mostly on ebay). I really don't need or want sites adding such functionality for me (especially if I'm running Cooliris)
It really reminds me of the midi files and flash tags of the mid-90s. It looks kinda cool the whoever wrote the site, but kinda sucks to anyone reading the site.