One consideration is how much control you give away when you take funding. If you retain control of your board, and generally take beneficial terms on the funding, it doesn't have to change the way you run a bootstrap business. Case in point: 37signals.

There are money other examples too. I know a very popular business that is successful, VC funded and will likely not have an exit because the founders retain control and they don't want to do that. There are other options (dividends, secondary markets) that can give liquidity.