This is the wonderful grey area - if you pose no threat, no harm, and it's deemed as harmless and if anything promotes themselves, there is no worry, it's just a huge grey area - I'm sure if someone set up a forum and then just named it uk webmaster world, and utilised all the SEO used on this site - people might gettle a little miffed - but there would be no real legal standing on it.
Lego managed to win a case against someone using their product in some videos, but because it was deemed that the vids weren't in Lego's clean nature they had to drop the lego brand name from the title. How many of us ask for a 'biro'? or go to 'hoover' the mess up?
It's a huge grey area, and I'm sure in time and I'm sure there have been some cases in court to argue such things, it's a case using some common sense, and thinking correctly, there's no point in getting into arguments, or annoying other people or landing in a legal battle - especially if it's for a little bit of PR etc.
Wasn't there a similar case where - I think it was Microsoft threatened legal action against a 12 year old in Canada about the domain name or site he was running - can't remember the fully story, maybe someone else can remember - but it's a similar thing. There's no harm, if it's doing no harm.