Do you use Google Reader for reading blogs and newspapers? If so, you have probably experienced its "Friends' Shared Items", a nifty little feature that could be the starting point for converting Reader -- or its variant -- into a social networking site. By sharing some interesting stuff, you allow it to be seen by those on your network; you can also exercise some fine-grained control over who gets to see what; see here and here for more details.
The best thing is this: sharing on Reader doesn't require you to send e-mails, or to use social bookmarking sites or Facebook; just one click that says "share this item." Easy, no?
This is a wonderful way to spread great ideas -- blog posts, news stories, longer articles, just plain memes. I have found some very interesting stuff through this feature, and I think it's fantastic. Today, for example, a friend shared this PhD Comics strip which deserves to travel far simply because it gives PhD advisers everywhere some ideas about how to torment their students ;-)
Do you use Google Reader? If so, do please turn this feature on, and start sharing some links; when you do so, please include me in your network of friends ...