I ran across this video a while ago on what can happen to you if you don't pay your taxes. At some point during your Bitcoin career, the cryptocoin will be converted to fiat and that's how they will catch you.
https://www.youtube.com/watch?v=hf2fNEUPjQwIt depends on which resident you live. In many places, it is easier to not pay tax because the government does not have enough power to control citizen. In someplace such as Spain, people are struggling about tax and you can see that many football players have to stand trial because they are found not paying enough tax