(No, I’m not dead, and this hasn’t been abandoned, I may even start posting semi-regularly again!)
A few centuries ago in Europe calling cards (also known as visiting cards) were popular in Europe. There was quite a lot of etiquette around the use of calling cards which were primarily used to announce the intention to visit someone. Also popular a generation or two ago were autograph books, another similar form of social ritual where visitors would record their visits in a book.
With our global society now and busy lifestyle, this niceties are impractical. However, it’s interesting to see amazing success of MySpace (hey, you never predicted it would get this big either!) which in some ways bears a resemblance to these social niceties of old, although with many differences as well of course. Any technology that allows people to interact socially with their friends stands a great chance of success.
There has been a heap of photo sharing sites, but flickr with its clever integration of social networking and folksonomies has taken the photo sharing space by storm. Likewise with YouTube.
It’s so easy to get carried away with technology, web 2.0, tags, folksonomies, and all that sexy stuff, and forget the big thing: people want to connect with other people. Make that happen, and there’s a good chance you are onto a winner.