monero has become popular in this space, but the average (illicit) user is still probably making operational mistakes while buying, using, and selling it. in the case of monero a lot of people like to skip the step where they download a 30GB+ blockchain over tor, and I can't blame them. when the privacy-oriented cryptocurrencies are effortlessly private, that's when they will have arrived so to speak. I'm fairly optimistic about moxie & co's recently-announced mobilecoin (https://www.mobilecoin.com/whitepaper-en.pdf) for that reason -- if it's going to get adopted by whatsapp, the user experience will necessarily be pretty darned simple.