I could be completely wrong here, but isn't it a pretty big risk to start doing actual business (i.e. selling your stuff for money, using your personal bank account to cash your business' checks) before you incorporate? Because at that point, if there is a legal dispute can't you be held personally liable and get really screwed?

I'm imagining a scenario where you have some sort of SAAS that a customer uses, then there is some issue (could be real, could be made up or the customer's fault, but I doubt a court could tell before trial) and the customer sues you for some huge amount of "potential lost revenue". Just the pessimist in me talking, but I'm pretty sure I've read before about things like this. Incorporation is so cheap, I don't see why you wouldn't just do that right before you start doing actual business to protect against this scenario.