Even outside of the VCs, it's true that startups generally don't get to hear negative feedback on their idea from anyone. On the whole, people are really nice. No one wants to say "I don't think that'll work because X" as, in other other sphere, it's just a really horrible thing to say to someone. Startups actually need to hear that stuff though. It's not horrible to tell a startup you think there's a barrier to their success; it's damn useful information.

It's a shame too, because I'm sure there's a lot of startups that could have used some honesty from the people around them early on to modify and pivot and consequently not fail.