Here in Silly Con valley it happens alot. Remember anyone can sue at anytime they want and make you defend yourself. The question is not if they can sue, but does their case have any merit?
Furthermore it also has to do with related businesses too, if somebody can show that they had a track record of a business name similier to yours you may be required to give up your TM even if it gets reg'ed.
This is a deep legal area that I am not 100% expert on and that is why patent and TM attornys make so much dough. That is why most photographers use their name it offers some protection that way. I use a fictitious business name too reg,d in CA so far after 20 years no issues. There are several similier names all of us too small to care.
Les