basically, just try not to piss off whoever is watching?
Basically, anyway. Also try not to make money off of someone's trademark if you
don't have their permission, not even ads.
(Finally posting after lurking for a long while.)
Perezhilton.com best example of how to skate around the issue, go to USPTO search the mark. copy and paste it in the number 5 option and you can see all the legal wrangling he did, basically his argument was "hey a gay Puerto Rican with a similar name has no resemblance to a fashion model Paris Hilton.
Im sure it's not that simple.