The latter. Leaving hunches and feelings aside, I'd point to a piece of anecdotal evidence: There was a This American Life story some time back about the life of some drug dealer/pimp in the 80s (or 70s, can't remember). As an aside, he told the story of the "genesis" of a prostitute. In short, he showed how, by gradual emotional manipulation through her boyfriend, they turned a "normal" girl that hung out with them into a prostitute.
I kind of cling to that one story, because it answers a question that I've had for a long time. Given that you're prostitution is not your dream job and that it is generally shunned by society, how does one become a prostitute?
For simplicity of the argument, I've assumed that the professions of pornographic performer and prostitute are mostly similar.