Beyond Facebook, there are several other sites I use frequently. Google, obviously, is necessary for when I want to search and email other people. Last.fm has slowly become my choice for listening to music and finding new bands. And recently, I joined Streamy for reading newsfeeds. These sites are all networks: usually, Last.fm is the only place I need to go to for music information. And I’ve never had to resort to a search engine past Google for most of my general needs.

There are some networks I don’t feel the need for anymore, however. For instance, when I feel the need to talk with moviegoers, I don’t use a specific web site: I just use the Flixster app on Facebook. It’s a full-fledged movie network, and it integrates perfectly with my already-existing profile. Similarly, whereas I once used a set of sites to find music online, now I just use Skreemr.com‘s app to find and save songs. That’s not quite a network, but it’s a full new set of functionality for Facebook. The same goes for Box.net‘s Files application, which has replaced my need to use the original Box site at all.

Rather than trying to be a network encompassing certain features – photos, events, groups – Facebook has turned itself into a directory of features – their apps. By letting sites use their features on Facebook’s main site itself, it turns Facebook into more than a social network: it makes it a network of other networks, all co-existing with each other.

Of course, this isn’t a given: Last.fm has an application on Facebook, but it’s nowhere near the equivalent of using Last.fm’s web site itself. It’s up to the company to decide whether or not it wants to truly integrate itself with Facebook. Either choice has its advantages and drawbacks. Integrate with Facebook, and a smaller network is capable of gaining a much larger casual userbase than it might be able to attract otherwise. However, Facebook puts severe design limitations on companies that try to release their products. It’s hard to imagine a site like Digg looking nearly as good on Facebook as it does right now.