Touche, great answer. This is difficult though, lets say I was making a social networking app (massive cliche I know) - speaking to friends and family is out of the question as they would err on the side of being supportive as to not offend me.

I guess my other option would be to post on forums, but that would risk my idea being spotted by another developer.

Perhaps I could speak to the other startup founders I have met and spoken to in the past? Would the opinion of a startup founder be valid?