"Social Networking" sites

[Denny]

On Thu, 2008-04-24 at 13:09 +0200, Dave Hodgkinson wrote:
> Have I missed any important ones from this list:
> 
> Mypsace
> Facebook
> Linkedin
> Ecademy
> dopplr
> last.fm

> Ignoring bebo and dating sites obviously.

Also ignoring LiveJournal and imitators?

How about microblogging communities such as Jaiku and Twitter?

Media-focused sites with group/community features, e.g. flickr,
youtube...?

http://en.wikipedia.org/wiki/List_of_social_networking_websites suggests
Advogato  :)  (okay, you said important)

It also suggests Meetup, which may be 'important' enough to feature on
your list...  I've run across it being used in a few different social
contexts, both professional networking and hobby stuff.