People that care about you (parents etc) are likely to like your idea no matter what, friends probably fall into this too. When someone says "that sounds like an OK idea" most people hear "that is the best idea ever". At the other end of the scale some people just don't listen and are negative, they cannot immediately see how it will work and dismiss it as a bad idea. And with regards to things like Mechanical Turk, if your product is really targetting people who are willing to answer questions for a few cents then great, but in general I can't imagine it is that useful.
Pitching and validating ideas against people in your real target market is a good start, but even then there is a massive difference between saying they'll pay for something and actually paying for it. If you pitch someone an idea and it results in useful questions and a level of excitment then that is a better indicator, if someone says that sounds great and then starts talking about something completely offtopic then I would say that means they don't really believe it.