I lost one of my domains last week. I received a cease and desist letter from one of the largest companies in my niche claiming that my company's name infringes on their trademark. The names were somewhat similar, but my name clearly wasn't based on theirs. I probably would have won if it went to court. They are a multi-million dollar corporation with in-house attorneys. So I decided it would be cheaper for me to change the name of my store. Kind of sucks about of year of work is down the drain. We just started to rank and get decent traffic (I'm assuming that's why they noticed us). But now they made it personal, and I'm more determined than ever to dominate the niche. So the moral of the story make sure you use a unique name that is nowhere close to what your competitors are. Cheers!