From my experience, the problem is that when your strategy is chasing big customers v. small ones, the customers you often end up with are the worst of both worlds - they are large enough to act like big customers (want contracts and features outside the scope of what you are working on), but will only be looking to pay prices that small companies need. I worked at a company in that spot for a while. In SaaS, sales teams can play a big role, but until you have a pretty decent cashflow, it makes more sense to me to have them focus much more on inbound sales (and account management) than outbound, which is a very different sales model. Eventually, once you hit a certain size, you probably need a real sales team, since that's what will close the real big fish. But before you go after them, make sure you have enough cash flow that your boat doesn't sink before they can reel them in (to continue the fishing metaphor).