Googles's Social Graph API
The Google Code Blog introduced today the Social Graph API which is meant to make the information of a social graph to be reused easily. It's based on the open standards XFN and FOAF data that is embedded into websites. You can find some simple toys to get the idea at the project page. It is real fun to play around with this! Tim O'Reilly asks for mechanism that enforce privacy about selected connections what I also really would like to see. I am not sure but I think it (actually not the Social API itself but XFN/FOAF/etc. in general) also offers new ways of spamming: An advertisement site could like to random profiles pages as friends and if the linked person checks their graphs (asking for people who linked to them) they see the link. Not sure if I got that wrong. Anyhow, this stuff looks really interesting and promising!