Here is the Federal Code that seems to be applicable: http://www.law.cornell.edu/uscode/text/18/1952
After reading this code it appears that the owners of myredbook need not be actually the people convicted of the illegal acts which are illegal by California state law. The owners of myredbook only need to facilitate the illegal acts of others. Since some posters / advertisers on myredbook have been convicted of prostitution this is likely the basis of using the California state prostitution laws in the myredbook owners federal indictment.
Furthermore, since the owners of myredbook used an interstate means, the Internet, and transferred funds between banks, maybe, in different states. This would be the other basis necessary to violate the above referenced federal law.
So it looks like the myredbook owners may be in pretty big trouble.