What are the implications for UK born entrepreneurs looking to start in the US. Is a visa needed?

Ask the founders of auctomatic; they're currently doing it.

Someone I knew in Hong Kong researched this, and he said that if you can deposit $x in a U.S. bank, INS will give you an "investor's visa".

I forgot what was x was exactly, but it was six figures, IIRC.

Then again, that was a while ago (pre 9/11, when some immigration rules were changed), so you may want to confirm that program still exists.

Ok interesting stuff - thanks for the replies. Does anyone know the guys from auctomatic post on these pages at all?