People networks - where to register?

We are in a time of so-called social services being as abundant as never before. Which means that every week there's an abundancy of services with the basic idea to connect people. As it seems difficult to know where to register (I just joined the third virtual media shelf and am starting to loose track on how many services I am registered to at all), I would like to propose the following characterization:

• Media-based recommendation networks - aggregate books, music and videos you own or like to find people with similar media consumption preferences and have the service recommend other media items or people with similar (media) preferences. Examples are librarything, shelfmates, moviepilot (in German),only to name a few
  
• Sequential media recommendation services: specify a preferred media item and have the service recommend you similar items, such as last.fm or Pandora
  
• Location-based networks - share ratings about localizable entities (e. g. shops, restaurants, monuments, museums) and use the service as a kind of collaborative tourist guide. These service are often available in web-based and / or mobile versions, and some of them include automatic localization. Examples are qype, qiro, townster.
  
• Offer-and-demand-based networks - share your professional experience, your hobbies or your needs in order to find what you're looking for, e. g. a new job, a relationship, a professional (e. g. craftsman) to get a job done, etc. Examples include Xing, LinkedIn, MyHammer (in German), Friendster, not to mention the zillions of dating platforms.
  
• (Micro)publishing sites, such as weblog hosting services, twitter or jaiku
  

I am not sure where resource aggregation services for photos, videos or bookmarks fit into that classification, as the social network and recommendation factor does not seem to be prominent with regards to services such as flick.r, YouTube and del.icio.us.

Also, as this is only a first attempt, I do welcome comments that are geared towards expanding this classification. More specifically, does anyone know of other attempts to classify all these fancy services that claim to be Web2.0?