We discussed this on IM last night, and thought it was worth throwing out for conversation. My musing is such: I've bought and read some of those 'erotica anthologies', and for the most part, they bore me to tears. So I've been wondering if there's a component of having an attachment to a character that adds to the enjoyment of such fic. As in: I find I enjoy 'adult' fanfic with a character I know and care about more than the 'professional' sorts of stories found in published anthologies. With many of those, it's virtually nameless and faceless and I just don't care enough about the participants for the story to be satisfying on any level. Obviously, there are exceptions. but generally speaking that seems to be the pattern.
And here's hoping the other participants of last night's conversation share their thoughts.