WinFs, Aero and Hailstorm
Remember Project Hailstorm (later called My Services)?
It was that MS project that suggested having all your personal data (documents, contacts, calendar, etc) aggregated in centralized servers so it would be accessible from anywhere, and that was cancelled because everyone got worried about having their data in Microsoft's servers (even if this was not required).
WinFS/Aero seem to target the same problem but from a different perspective. Instead of having that data in a server, you have it in your own box, so everybody feels better. What they did is to have a central local storage for that data instead of having each application provide its own.
If you add WinFS synchronization to the picture, then it's pretty much the same as Hailstorm. You will be able to keep all your data in a server and synchronize it to your local machine. I guess we'll see some activity in this area when Longhorn is released, like MS providing a way to store that information in their servers, in third party servers or in your own corporate servers.