[noduerme]

re: UPDATE: apparently the entire concept of their app is a direct rip-off of mine, not just the name. I guess that makes the legal issues more interesting?

It might. Don't go on a spending spree yet. Let a competent lawyer look it over. My guess at a glance -- and I'm not a lawyer, just stewed in IP issues -- would be you'll have a hard time getting anything out of their theft of your concept, short of owning a patent. Copyright could give you some relief if they directly ripped your code off and you can prove they decompiled and/or used something from that. Your best bet again is probably trademark infringement against your mark which had prior use. (That also depends on if Facebook themselves haven't trademarked the word "Like" the way they've trademarked "Book".)

Other than a lawyer, your only bet is to raise an unholy racket here and in the blogosphere and make sure everyone knows you did it first. Which I fully support.