[visural]

I don't list my interests on my facebook profile, nor do a great many of the people on my friends list. For some that is because they don't want facebook having this information, for others, they simple can't be bothered entering it.

I don't think you can classify this as "using it wrong".

It seems obvious that if I or a user like me were to use this service it wouldn't work very well, and would potentially devalue the service for other users (through poor matches).

The developer of the service is artificially limiting their market by only allowing Facebook Connect and they may have problems getting the necessary critical mass for the service to be useful as a result. I don't think it's trolling to make this observation.

[gfodor]

You (and your friends) are in the stark minority. I worked on a product that drove product recommendations using Facebook interests. It worked great. People list their interests on Facebook because they want to personalize their profile page and share their interests with their friends.

When you create a product like this, every decision you make "artificially limits" your market. But often these decisions open up other parts of the market that would be inaccessible otherwise. For example, the time they would have spent on building alternative login options for people like you would probably be better spent adding features for the people who have no problem using Facebook connect, and who list their interests on Facebook.