[jlees]

Visa problems as already hinted, plus how will you fund yourself while there?

There are quite a few schemes over here that will support starving students starting businesses, then when you have a little more of a solid footing you can hop over to SF and go crazy.

Not sure why you think it's a closed door policy here, I've had great success and loads of feedback from throwing my idea out there; it's undergone a lot of transformation in the last 8 months or so, to the point where I think I'll now get the most out of it going abroad. If I'd gone to SF last summer I don't think it would actually have helped that much because I wouldn't have been able to stick around, and meeting people once with a bright idea only has so much impact.

On the flipside I'm sure if you have the resources to stay in SF for a while you can get some great feedback, maybe find people to team up with, etc. I'd just be really wary of the financials and visa situation.