On Dropbox's a user by name of Chen S. wrote, "My big concern with Google Drive is that they already have all my emails, web analytics, and search terms. Do I really want to give them even more data?"

Another user, Christopher H., said this in the Dropbox forum: "Like many other users, I'm not excited about Google having more data points on my life via the files I will be storing in their cloud."

Still another Dropbox user, -- Mark Mc., noted that while Google might not sell or disclose data without a user's permission, "they can, however, use that data in anyway shape or form the like internally - and if that includes selling personalised [sic] ad's based on data farming of the files that I've uploaded I'm out of there!"

But a Google spokesman said Drive's terms of service make it clear, "what belongs to you stays yours" and the company's policies are no more onerous than other service providers.

"You own your files and control their sharing, plain and simple. Our Terms of Service enable us to give you the services you want -- so if you decide to share a document with someone, or open it on a different device, you can," he said. "Many who have covered this simply ignored that paragraph and quoted only the one immediately following it, which grants us the license required by copyright law to display or transmit content on a user's behalf. Other companies use very similar language."