It seems likely that the tether company is a fraud, given the size of their January print runs. It seems likely that not only has tether been used by its owners as a way to prop up crypto-currency prices, but to acquire bitcoin and other coins under false pretences.
There's no proof either way, but the lack of audit is very, very fishy.
Further, I watched the USDT/USD market on kraken on Friday.All morning there was downward pressure, buy-walls of millions of dollars were eaten into and destroyed over the course of a few hours, until there was no bid volume at all down to about 90 cents.
All of a sudden, in the course of about two minutes, a rapid cascade of very small trades (a few tens to a few hundreds of dollars) propelled it back to ~98.5 cents. It looked really dodgy.