I frequently see people posting in the Google Sites' help forum that they are unable to access their Site and are frantic because their business depends on it.
While I have sympathy with these people it is a salutory lesson that anyone running a business should learn. TANSTAAFL - "There ain't no such thing as a Free Lunch".
If your business depends on your website you really should not rely on a 'free' service that has no service level agreement (SLA) and no online or telephone support.
That said, Google Sites can be a very cost-effective solution to providing an online presence. And a few very simple steps can make your investment much more secure and can be summed up in five words:
Use Google Apps for Business
See this article for more details: move site to apps