For the B2B project I would estimate between 10-15 clients before we committed ourselves, and once we had that info we surveyed about 25 potential customers (10-15 of which were in the first casual group).

For my current project I have spoken with at least 50 people. based on the recorded feedback I have. I would estimate about half the people I talk to have something to say either positive, negative, or both. But we haven't done anything in depth or official for this consumer product.