Cute doesn't cut it when people are relying on your business. I sure hope no SaaS vendors take this approach.
If your business is providing hosting for content or providing a service that is expected to be ubiquitously available then QoS is a significant part of your business whether your service is nominally free or not.
Edit: Whether your revenue comes from users or from advertisers the reliability and quality of your service matters. If your userbase decides to abandon you then you are screwed regardless of whether they are your customers or your product.