This could be a factor but I'm not sure that this is the complete picture. Having lived on both sides of the Atlantic, I would say it felt much easier to start

This could be a factor but I'm not sure that this is the complete picture. Having lived on both sides of the Atlantic, I would say it felt much easier to start a business in the UK: Healthcare is covered, believe it or not there is less bureaucracy, there's great digital banking options that the US is only just getting its head around, etc. In Europe I always felt I had a safety net to fall back on if my business failed – not so in the US. My own hypothesis is that the European stock exchanges aren't a particularly attractive place for an IPO. London's AIM, isn't quite the NASDAQ. The US tech stocks are now worth more than the entire European stock market according to Bank of America Global Research. And so I think it's always in the back of a Founder's mind – not to mention their investors – that they'll have better liquidity if they're packaged as a US inc. to start with – and if not just sell to one. Hopefully with Sequoia opening an office in London though, this will begin to change.