They have charged Kim Dotcom with the same offenses for running megaupload, and I think that they chucked in wire fraud as well.
It's worrying how vague these 'crimes' are, it tips the balance of power too far in the direction of the government agency.
Doesn't matter if you're innocent or guilty. Game theory (born out by statistics) says you take the plea.
If they made me king tomorrow the first thing I would do is make plea bargains illegal.
This looks to be a charge under the federal Mann act (https://en.wikipedia.org/wiki/Mann_Act), which criminalizes using a facility of interstate commerce (i.e. the internet) to promote any sexual activity for which any person can be charged with a criminal offense. That offense would be the CA law against prostitution 647(b) (http://law.onecle.com/california/penal/647.html)
The Mann act has an ugly history of being used to convict all sorts of consensual sexual activity. For example, black men with white girlfriends (against state laws criminalizing interracial sex), and even sex outside of marriage (against state laws criminalizing adultery and premarital sex).