Or better yet, FourSquare. Square has a trademark[0] on using "Square" when describing "computer software for determining and mapping the physical locations of consumers;", yet they were given the trademark, even though there could be clear confusion, based on the legal wording.
The obvious answer is that Square has lawyers that found all the possible ways they could trademark the word "Square", even if the connection is highly suspect. Now they are using it to take down companies that cannot afford to defend themselves.
[0]http://tmsearch.uspto.gov/bin/showfield?f=doc&state=4809:16h...
My advice was specific and achieves the goal of not going bankrupt for a startup. I have been through lawsuits before and I know how expensive and distracting they can be.