CircleID

Hardly a new thing, I experience this over 2 years ago.
I had a third level domain off start.at (NAME.start.at or start.at/NAME)
I won't mention what NAME was (at it now goes to a porn site and I don't want to promote it) but since it a geographical region, rather than a brand name, the only action I took was to search for URL's that were pointing to it, and sending them an update informing them that it was no longer valid and to please update.
Unfortunately there are still some links pointing to it as some people just don't update their sites.

Ali, how much to you charge for advertising space?

Do you quality check any claims made?

Anybody with any domain can create subdomains of it, some of which might infringe on somebody's trademark.  That's not really something you can do anything about, except for after-the-fact action against somebody actually using such a name in an abusive way.