If you look at one of LinkedIn's alternate applications, LinkedIn Contacts, http://contacts.linkedin.com/ it actually is a light-weight CRM application. The CRM meaning, it automatically connects to your email and calendar to your LinkedIn account to know when and how you are interfacing with people. I get a daily email with the meetings that I had the day before about who I met, as well as information on their LI profile about the last email conversation I had with them. This is super nice if you meet a bunch of people and need a way to take notes on who they are and what they are doing, independent of their business card.

The contacts application also sends things like reminders for your contacts work anniversaries or when they change positions (something that you can't access in the LI API).

I sometimes think that I shouldn't be giving LI all of this information, but this is a typical case where the benefit received is greater than my privacy concerns.

Isn't that the whole point of Rapportive? They're the only company I can think of that has successfully solved the "social profile matching" problem that I can think of off the top of my head.

Ark does, and with significantly more data.