Extortion. "You keep using that word. I do not think it means what you think it means."
Mt.Gox failure to disclosure their identification policies in advance may be shady, hell it may even be illegal (doubtful) but under no possible interpretation of any law is it extortion. Even if it WAS extortion that is a criminal matter. You can't seek civil damages for a criminal charge. Even if a judge ruled that MtGox can't ask for your ID you have suffered no damages (legal sense of the word). You can't seek redress for damages never suffered.
Under the totally implausible scenario that anyone took your case seriously, and you made it to court, and survived motions to dismiss, and ended up winning at best you would get your $100 back (maybe with some interest and no not that 1% per day interest in the lending forum the 1.5% APR interest you could claim as damages). So in a year you might get $101.50. Well no you won't but that is under the most asininely optimistic scenario you could possibly hope for.
I don't think you read my post above when I said:
"I would not have to prove this in a court of law as I am not suing them. But I do intend to file a formal complaint with the Attorney General of my state and with the emails they have sent me repeatedly asking for my personal ID for my $100, that is enough to get the formal complaint to stick with extortion in the record."
Before getting all high and mighty on me like I'm the idiot for suing for $100, please note that I explicitly state above that I am not going to sue them. Why would I say that I am not suing them? Because that would be an asininely optimistic thing to say. The point was to convince others to file a formal complaint with the state Attorney General that MtGox stole $100 with this same method.