I've heard elsewhere that this is largely an urban legend, that there is no "honor among thieves" in prison.
Trust me, it's no urban legend.
I did a short research at Google. Couldn't find stats for rape of child molesters. I did find the rate of state prison rapes was 0.5 per 1,000 inmates (Aug 05 report).
http://feministing.com/mt-comments.cgi?entry_id=1718
We'd have to know the rate for incarcerated child molesters, which I couldn't find, in order to see how many of those perverts were being raped in prison. I still don't think it's a high number.
Oh well, it's not an important issue in my life. But prison rape of any kind is horrible and should NEVER be allowed.