Advertising your dating site
Theme sites work VERY well, because it allows you to target one specific audience, instead of the entire world. Allowing new members to gain access for free, will definitely attract many more people to try your services out before they go to another place.
Many of the bigger dating sites allow their larger affiliates to rebrand their site -- that is one reason it seems like there are way more dating sites out there than there really are. I would not let anyone tell me that it is impossible to do. You might just need a different approach to get started or the funds to push a new brand into the market. I know it's a flooded market and I do have somewhat of a niche.
For new dating sites its hard to get members because there aren't any other members for them to communicate with.