I think that most people who decide to receive a professional tantric massage might end up being rather surprised by some of its effects.
The thing has a tendency to stir up strong emotions.
I mean, really REALLY big feelings. As in, while I'm laying there, there's always a point where I'm completely overwhelmed with love. Where I want to tell her how much I'm in love with her, how beautiful she is, and so on.
Of course, I know that the feeling goes away after the session, and I know that it is not "real", in the sense that I'm not really in love with my tantrika. We respect each other, I rather like her (though I often disagree and have a hard time not rolling my eyes when she starts about energetic esoteric teachings), and we have lots of fun, before and after and during the session. (Though that last one's a totally different kind of fun.)
I can totally see how this may overwhelm and even overtrain some clients. Especially if they're lonely. Especially if they're somewhat socially awkward. Even more so if they really have no idea what tantra is all about. So I guess... quite a lot of the clients of such an establishment, actually.
So I guess that the practitioners often receive all kinds of fantastic offers. Some of which may be tempting. (Quoth my tantrika: "You never start a relationship with a client. It can't work out." Intelligent woman, she is!)
Basically, there's a guy who receives heaven from your touch, and who is probably prepared to give a lot for having this all for himself... in terms of money, but also of affection, devotion, time... I imagine that it must be extremely tempting to go on a power trip on one of those offers.
So I've started to write a story where that's exactly what happens. Where a woman is given the opportunity to work as a tantric masseuse, and that woman is way too young and naive (and, at that point, disappointed by men) to resist this sort of temptation, so she does go on this power trip, and it does not end well.
I think that this is highly realistic, and I'm pretty certain it has happened before. Not even necessarily with tantrikas...