If the name of your project is important to you, register a trademark (or actively use the name to establish a trademark). Without a trademark you don't "own" the name, and anyone can use the name for a similar product/service/etc...
Even with a trademark you don't 'own' the name, you'll have to go to court for every infringement, which is for almost anybody that does not have a very large business interest in a name an un-affordable option.
Also, given googles actions in the gmail.de case it seems as though they don't really care about trademarks anyway, they'll just keep on pushing.
