Uri Levanon visualized what I wrote about in my Skype as Personal Memory and Skype as Collective Memory posts. His designs highlight alerting.

This diagram shows a reminder in the Skype contacts tab tying a to do list and tags to a contact.

This mockup shows the same reminder but in your Outlook Inbox.

When we talk about the value of social capital, alerting like this helps us exercise our relationships and do the most we can for our friends, families, and colleagues. You really must see all of Uri's visualizations and his walkthrough of this user experience.