Tried one of these sites (can't recall which one) a few years ago. Signed up, free, and received a message from a supposedly local girl. Could only read the message by making a payment. Paid, not much, no reply from the female.
Little later noticed she was appearing at opposite end of the country. Although I hadn't lost much money decided to see how far I could get by making a complaint, threatening to complain to card company I'd used to make the payment that it was all a scam etc. After some time did get a response, and can't recall all detail, but should be noted that the females receive a referral fee for every sign up that they've been responsible for.