My experience on zoosk has been beyond frustrating, as:
1. The site is very contrived with all of the inadvertent "views."
2. When I have sent gals messages, I get a notification that they have either "accpeted my chat request" or that they "want to chat" with me.
3. I got suckered by the "mega flirt" feature, as I did notice that two ladies sent me the EXACT SAME message. It was not until quite a while later that I realized the why of that, and it was a result of seeing the template options in the "mega flirt" section (I also saw another, different exact same template message there, which I had received from another gal).
All of the above listed reasons detract from any credibility that this site might have.
Granted, I did have what appeared to be legitimate conversations with a few gals, but the absolute sky-high rejection rate has been staggering, and I am a pretty decent looking guy. As has been mentioned by others, my guess is that the vast majority of women are not paying members, if real at all.