[Zak]

A way might be to simply limit the number of topics and industries a person can list, though that has its own downsides.

Just thinking of my own case, you won't get much of use from Facebook (I post pictures of kittens and cookie recipes), twitter (It's been nearly a year since I've tweeted anything) or Linkedin (I barely use it). You'd get more of use from HN, reddit or (especially) github, but it might be harder to extract useful information from those sources.

[lucahammer]

We will definitely add more services in the future and you are right that these three were the easiest to start with and give ok results for many people.

You could still provide buyers with awesome cookie recipes!