One of the more frequently asked questions about switching to Google Apps for Work is concern over data security. The two main concerns are, (1) Is my data private and who owns the data? The second main concern, is, (2) How secure is my data once it is stored on the cloud? Watch this first video that discusses the privacy of your data and who owns the data (Google is legally prohibited from accessing your data):
This video below answers the how secure is your data once Google stores your data on the cloud (most companies cannot afford the data security provided by Google) in the Google Data Security:
Google Security White Paper
Finally, read the Google Security White Paper that explains clearly how your data is safe.