I'm in a similar boat. It really depends on how marketable your name is.

In my case, I made it up. I'm planning on getting a trademark before a full launch. They key point about trademark law is that it's hard to defend it if you go a long time and allow others to use it.

BTW, there's a good law question & answer site that you can ask your questions for free: http://www.avvo.com/free-legal-advice/Trademarks/ (no affiliation w/ me)