Trademark isn't there to prevent theft of brilliant brand names; it's there to prevent confusion. That's an entirely different endeavor than either patent (protecting ideas) or copyright (protecting creative expression).
This is a lost truth on most people. If something trademarked can be used in a context that does not result in the consumer being confused, then the owner automatically loose the trademark. Its a consumer protection law, not an anti-competition law.
This depends, I think. My understanding is there are some caveats when something gets really well known, sometimes for the better and sometimes for the worse. Trademark law isn't always executed perfectly (see some of the behavior of the Olympic Committee, for instance). The fundamental purpose, however, remains to avoid confusion.
