I dunno about the legal issues, but
this site about a phd student at my college has been up for a few years and no-one's got into any trouble over it. I guess it depends whether it's really malicious, or just poking a bit of fun at the person concerned - often a fine line, I know.
I guess if it really was serious, then there could be lawsuits - probably comes under defamation I guess (something along the lines of making comments that might cause right-thinking members of the public to hold a lower opinion of the person concerned). Probably a bit risky, especially if the person concerned is the sort that might be happy to file a lawsuit. You'd probably be much safer doing it in the UK, where people seem less ready to run straight to the courts at the slightest sniff of money...
