What everyone needs to keep in mind is that the entire point of blockchain/DLT technology is to maintain a permanent, immutable, publically distributed ledger. Re-read that last part.

This means that the IRS has all of the information they need to track down people avoiding taxes and prosecute to the full extent of the law, which they will undoubtedly do. It is all about maintaining their tax base and their sense of control. This isn't just fear-mongering either, this is a simple fact of governance going back all throughout humanity.

For those in the space who still believe that they (the IRS) cannot fully track down users who use TOR, VPN's, and any number of additional layers often cited, you are mistaken. TOR has proven to be breached, as have VPN's, the international standard for WiFi encryption, etc. In the world of cyber, state-backed entities are not the entities you wish to go up against. They have infinite resources to throw at you. The IRS is the definition of state-backed as they are the government's debt collector.

Not to mention they have publically stated they are working hand in hand with blockchain auditors and are actively employing blockchain engineers in relatively new positions.

http://fortune.com/2017/08/22/irs-tax-cheats-bitcoin-chainalysis/

https://www.ethnews.com/six-us-government-agencies-hire-investigative-blockchain-firm-chainalysis

Highly encourage everyone to consult with a tax professional should you be sitting on cashed out gains. Shamelessly upvoting my own comment here because I think it's very important people understand this!