The terms and conditions for brazilian users tell exactly this, more specific the section 5 that in english is 195 words long, but in portuguese is 764 words long. And thats not just because of the translation, this part goes into more details on what they do.
"In order to allow guests in our site to experience the kind of communication they expect as members, we may create profiles that may interact with them.
The purpose of us creating these profiles is to provide entertainment for our guests, to allow guests users to explore our services and to promote greater participation in our services. The messages sent are computer generated. The messages from the profiles we create try to simulate communications so you can also become a member, pushing you into participating in more conversations and to raise interaction between friends.
You acknowledge and agree that some profiles published in the site, with whom you may communicate as a guest, may be fictitious. The purpose of the creation of these profiles is to provide our invited users with entertainment."
So, at least to non paying users its clear that a lot of the females users and their messages are computer generated.
More here in Portuguese: http://gizmodo.uol.com.br/term...