The company is saying that Gmail and Picasa storage can also be used. Google Docs Product Marketing Manager Peter Harbison writes:
Each account will get 1 GB of free storage in Google Docs (in addition to the 1 GB of free storage in Picasa Web Albums and over 7 GB of free storage in Gmail) and will be able to upload any file up to 250 MB. If you’ve already purchased additional storage for Picasa Web Albums and Gmail, that storage is now shared with Google Docs as well, giving you more ways to use your online storage space. As we announced in November, additional storage is only $0.25 per GB per year. And because of the enthusiastic response, the Google Photos team has extended the special offer with Eye-Fi: users in the US or Canada who purchase 200 GB of extra storage for $50 will receive a free wifi-enabled SD card from Eye-Fi.