Trademarks are inherently limited in scope. If I'm making widgets named FOO, and I've registered that trademark, I have no inherent right to FOO.com or @FOO or anything else that's completely general and may have nothing to do with widgets.

http://www.chillingeffects.org/domain/faq.cgi

> Of course, you aren?t expected to look up trademark registrations around the world or research legal issues like common law trademark rights. That?s why the Policy requires the trademark owner (the complainant) to prove bad faith and why the Policy offers domain name holders the opportunity to demonstrate that they have rights or legitimate interests in the domain name.

That's true regarding infringement, but trademark dilution can apply to uses that aren't in competition with or relevant to the trademark holder.

http://en.wikipedia.org/wiki/Federal_Trademark_Dilution_Act

The really difficult thing is that, while in many cases the demand letters are legitimate and appropriate, in some cases like this they aren't. If Zephoria sued danah for trademark infringement, I would certainly hope they would lose since danah can probably prove that she's been using the pseudonym since 1998, 4 years before their trademark issued.

Could it be that Tumblr handles are actually owned by Tumblr, thus it is Tumblr which was "infringing on trademark" and needed to act on Demand Letter? I would love if you or somebody else with more legal knowledge than me (which is not hard :)) can explain this.

If their legal department determined this is "valid" (assuming that means she is infringing on the mark, which is the only case in which I could possibly see not contacting her), their legal department must be staffed by baboons.

From my armchair lawyering understanding, the rule is that Trademark must actively be enforced or you risk diluting the mark.

However its not clear how strictly it must be enforced, unfortunately that means it tends to be enforced more strictly then is absolutely necessary "just in case".