This is what KLM Royal Dutch Airlines is doing: their incoming check-in system will allow passengers to choose seat mates based on their Facebook and LinkedIn profiles, so he or she would be someone who shares your interests.
That's not a bad idea. However, people will also be able to select seat mate based on looks, which is kind of weird. But don't freak out: you will have to connect your Facebook or LinkedIn profile to join this service.
I can see that it may be a good thing if you want to talk on your flight and perhaps jumpstart an interesting work connection or a friendship. On the other hand, I can also see this turning quickly into a nightmare, which is why I hope they include a "leave me alone" option.