Plain and simple.. this article around 3 days ago:
What it basically signalled is that the IRS is currently very keen and has announced that they will be tracking down those who are using Bitcoin to evade taxes. Bitcoin is in fact very traceable and there are AI and services like Chainanalysis to trace bitcoin transactions.
What they usually do is track down transactions up to the wallet addresses owned and operated by exchanges wherein these BTC are exchanged for coins. After which, it's simply subpoena time!
Now due to this a LOT of tax evaders or even simple US citizens are resorting to more anonymous coins like Monero. This signals rapid transition from Bitcoin to Monero and a lot of demand on exchanges such as Poloniex.
This news wave is one example
Wan't to know another cheap coin thats anonymous as well? Try NAVcoin! Happy Trading!