I think at first it doesn't matter. Facebook was originally thefacebook.com, delicious.com was del.ico.us, dropbox was getdropbox.com. I know those examples are all .com, but the point is that you can change your domain once your product gains traction and you have a proven product. Then you can spend the big bucks on the domain you really want.
...just check first that it's not a legitimate company using the .com address.