The interesting thing to me is that Gaydar was very successful in Japan, except it was marketed to straight people. Over 100,000 units were sold.
The reason I find this interesting is because a lot of the next-gen mobile apps show up in Japan first. Japan is way ahead of the USA in terms of mobile usage. I suspect a lot of people look to Japan for business ideas that can be adopted for the US market. I mean, if it worked in Japan, then surely it'll work everywhere, right?
Except it doesn't. Japanese culture is REALLY different than American culture. In Japan, you can get your nails manicured by a vending machine. Japan has a popular movie series called Rapeman, it's about a hero who rapes women who have spurned the advances of lonely salarymen. It was shown at the local cineplex.
Japanese have strict social customs. Every interaction is highly ritualized. I suspect the rising mobile culture allows the Japanese to circumvent those customs and that's a big reason for the popularity of social mobile apps. In the US, social interactions are not restricted. I want to talk to a girl in a coffeeshop, I say hello. No one thinks I'm crazy, unless I happen to be homeless.
My point is this: be careful when you look to Japan for the validation of a market, other companies have been burned, it might happen to you, too.