This is just my opinion, but every time I go look for a new name for a website I am going to put up, I make very sure that I get a .com and that the .net and .org variations are available as well.
Even if I don’t get the .net or .org, I am the first to have the top level which usually means im the first with that name.
This insures that no one will be in my way when it comes to a possible copyright/intellectual property infringement.
There’s no reason to ever buy a .net, or .org of a domain name that the .com was taken unless you are an organization and get a .org I guess, or you thought somewhere in the back of your mind that one day they may offer you money for it.
If you’re fairly new to buying domains, and the internet in general I can understand why you might have done that though. Let this be a 8.88 cent lesson to you. Give them the domain and only be out 8.88, or don’t and risk a lot more of a monetary loss.
Lawsuits aren’t worth fighting if you aren’t making money off what you’re fighting for.
Nathan