The first patent (the one filed in 1997) describes a PIM a la microsoft exchange. The second patent (the one filed in 1999) distinctly mentions relationships and granting permission to view personal information. The 2008 patent just seems to adjust the claims to fit a current social network.
Twitter doesn't store personal details. Even putting a name in your profile name is optional. How can they provide information they don't even collect?
Dropbox's beta builds have LAN sync.