Tether was investigated but nothing happened from it, it is still used as the most popular stable coin so i wouldn't call it a scam. ICOs need a lot of research, definitely not for newbies who just put their coins into anything and expect a profit
After they made their money from it they showed some financial reports, that should've done prior.
I'm not a legal expert so I don't know why nohting happened from those subpoenas, out of jurisdiction?