Let's say Mark Zuck. wants to use Google Drive, and upload all Facebook code on it. Using this TOS, it allows Google to go through the Facebook code, and use it to improve Google+.
As a programmer that uses Dropbox to backup all my code, I find this a little bit scary.
If you are concerned with storing your code on a service, perhaps you shouldn't store your code on that service?
The way I see it, they could go through your code and use your secret sauce, in secret. Now, with these TOS, let's say they are in the clear, legally. Now weigh the punishment Dropbox would receive for breaching your copyright, vs the punishment they would receive for using their users'/customers' data immorally, for their own gain.
As a programmer that uses Dropbox to backup all my code, I find this a little bit scary.