The
SL part is problematic in general but is easy to enforce if you go contextual. For example we can't argue that
SL in
SL Universe is not Second Life.
Having been exposed to trademark rules of international organizations, not even corporations, I'm actually surprised Linden Labs took so long to handle this matter. Trademark guidelines are important so that people can clearly and easily distinguish between you (
SL and LL in this case) and someone who is only associated with you (
SLU, SLExchange, etc). RIght when the commercial websites sprung up LL should have supplied logos (like the InSL) and usage rules for such purpose.
Truth be told, I was surprised that their logo/banner package that is downloadable from the website contained their
actual official logos and trademarks and not affiliation logos (e.g. InSL).