You data should always be in two locations...always.

Dropbox has the best sync tools going, but if you are a Microsoft Office user, you get 1 TB of storage included with their Office 365 software. As a straight backup tool, Carbonite is also a good solution.

We always recommend that our customers store a duplicate of their data somewhere, even though we provide online storage with our order management software. We believe this so strongly that we are building an integration with Dropbox services for our customers. (We are currently beta testing a uni-directional integration.)