If Google really means it, and wants it to be clear, they could put it right into the TOS: "Google may do X, when it does so in order to provide feature Y".
"The rights you grant in this license are for the limited purpose of operating, promoting, and improving our Services, and to develop new ones."
"Store your spreadsheets! Just like Joe Blow's 2012 sales forecast! (link to preview)"
eg. Rounding up non-gingers to be put in cages above pools of lava would be allowed
As a programmer that uses Dropbox to backup all my code, I find this a little bit scary.
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.
The bottom line is that you, as a user, have to grant such a license to Google, Flickr, etc in order for them to be able to provide the services that you want. Its a copyright issue, and I haven't seen any other good way around it in anyone else's TOS yet and I've read quite a few.