I'm a big fan of Google Docs for SME, having used it for two years in my current company, set it up for a startup project, and recommending it to folks starting a business.
While it takes away much of the pain and cost of providing these services locally, there is the nagging issue of not having a comprehensive 3rd party disaster recovery system in place. This was highlighted to me by a recent blog post from e1lven.com titled Why no company that values their data should EVER “Go Google”.
Google has a couple of stop gap, partial measures (like automatic forwarding of emails to another address). But there does not seem any native-Google approach to backup Google Apps data.