This probably differs from the system utilized in the Netherlands (where I'm from, obviously :)).
See, every revenue you might make from investing in cryptocurrency is seen as capital, for which you pay something like 1% according to the current legislation (I think that cryptocurrency-oriented legislation will take years to be developed let alone implemented, seeing as we still don't have a cabinet 6 months after the election).

So if you'd invest $1000 in bitcoin or whatever and the price soars and your investment is trippled, the taxes you'd have to pay would be roughly $30 as it stands now in my country. Therefore, I think that in the Netherlands the incentive to evade taxes on cryptocurrency is low as the taxes you'd have to pay are minimal compared to the taxes we pay doing our regular jobs (roughly 40%).