Whose to say they would pursue those charges? Why do they have to even disclose why they nabbed them? Under the PATRIOT act they can make anyone disappear without justification. Obviously if they're committing treason they could figure out any number of ways to make it happen.
Julian Assange is pretty high profile, considered a journalist by many, has run an organisation that exposed many legitimate scandals, etc. Celebrities also go to prison quite often.