MicroID

MicroID is a lightweight identity layer for the web. It is the sha5 hash of the sum of the sha5 hash of your email and the hash of the URL of the web location. It can be used to confirm that a specific web page is really yours.

It could be used for cross-networks investigations. Known MicroID providers:
 * Last.fm
 * ClaimID
 * ma.gnolia
 * Wikitravel
 * Del.icio.us
 * Yedda
 * Lingr
 * Jyte
 * BusyTonight

So it is possible to know when the user in 2 network is the same user and hence to do cross-networks investigations.

Check http://microid.org/

Also check
 * http://mashable.com/2007/09/10/online-identity/
 * http://b-side.com.sg/blog/2007/11/20_ways_to_aggregate_your_soci_1.html
 * http://www.masternewmedia.org/content_delivery_and_distribution/social-media/lifestreaming-aggregate-all-your-social-media-lifestreams-review-20071203.htm
 * http://bobstumpel.blogspot.com/2007/12/identity-20-110-ways-to-manage-edit.html
 * http://www.trustplus.com/
 * http://webworkerdaily.com/2007/06/29/3-ways-to-aggregate-your-identity/