If you’re out registering a dot-com domain, and an available domain seems too good to be true here in 2007, go see if it has any residual inbound links (use Yahoo!) or a history over at archive.org.
If you get a really coherent domain name, chances are it’s been used before. Now, sometimes you’ll be fine. Other times, just slam up a dummy page, get it verified via Yahoo and Google, and see if it indexes.
…and be ready to file a reconsideration request.
Most domains that are really coherent and dot-com and available in 2007? Probably banned at least once already, or used for a porn-squatter spam site. You’ll end up having to do some housecleaning.