it's not extortion because there's no demand for money, property, services. it's a breach of terms/contract issue.
requiring customers to waive the right to sue (without recourse)
won't be looked upon favorably by any court. if poloniex willfully violated its terms (eg refusing to pay creditors in spite of good faith compliance with their terms), or did so with gross negligence, that waiver will be laughed out of any respectable court.
writing an absolute bar to a lawsuit into a contract is totally unenforceable, period. not a lawyer, but i know that for damn sure. the only reason poloniex includes this kind of waiver is to deter gullible people from legal action and discourage them from even talking to a lawyer. it's not built to hold up in court.
the shadiest exchange at the moment is bittrex since they are still holding Syrians funds without paying them or even responding to their tickets
that's the breaks when you're a resident of a sanctioned country and dealing with an american company. i sympathize with syrians for sure, but the people running bittrex aren't brazen enough to violate sanctions.
here's why:
OFAC considers non-compliance with sanctions to be a serious threat to national security and foreign relations. Consequently, those who breach OFAC sanctions without obtaining the proper license can face severe legal repercussions. Fines range up to $20 million, depending the offence, and prison sentences can be as long as 30 years.
one of the things people don't get here, i think, is that poloniex and bittrex don't give a fuck about consumer affairs departments. they want to deter as much legal action as possible, sure. but they're probably much more worried about being accused of facilitating terrorism and money laundering, and i suspect federal law enforcement/regulators are in regular communication with them.