If the founders might be well-known (as was the case at the company I worked at), they might have been discussed in the trade press, as well as the mainstream p

If the founders might be well-known (as was the case at the company I worked at), they might have been discussed in the trade press, as well as the mainstream press like the Wall Street Journal. Also inquire with their coworkers or subordinates at their previous companies. Possibly you would want to do that anonymously, say by using a pseudonym when posting to a message board to social networking site.