I'm surprised no one has mentioned AshleyMadison.com
They've done a great job on the mainstream side and seem to have made a good push recruiting affiliates from the adult side too.
I like the direct approach they have with their marketing targeting the "cheaters" niche. After setting up a profile and taking a look at the site the profiles seemed to be more believable than most adult dating site. Also they limited their email spam to only a few a week rather than the usual 5 to 10 a day.
Hell I think they've even got Mario as their A.M. now.
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