I'v stopped people mid-pitch due to the fact that they are building something exactly like Blippy, Gowalla, Signpost, Chartbeat and Thumbtack (to name a few).

I'v stopped people mid-pitch due to the fact that they are building something exactly like Blippy, Gowalla, Signpost, Chartbeat and Thumbtack (to name a few). They always appreciate it, and in fact I've some say "I know, but can i pitch you anyway just to get feedback?" In those case I say "sure, but please don't tell me anything that's not obvious or public, because although I would never share what you tell me with an existing investment, I wouldn't want to have that appearance out there."