In two recent posts (Facebook sucks, The you-don’t-need-more-friends lobby, Robert Scoble has complained about the 5000-friend limit in Facebook. He said,

[…] it isn’t scalable and falls apart at 5,000 contacts. It pisses me off more and more every day because of that scaling wall.

and

Someone asked why I keep pointing out the 5,000 friends limit. Why? Because I still haven’t gotten through and I’m still getting pushback from the lobby. So, let’s try one more time.

I agree with Scoble to some extent. The issue is important: scalability, both in terms of network size and application quality across different functions is where sites like Facebook will live or die. Plus, Scoble is an edge case, clearly, and I always think edge cases are important for webapps to take into consideration as they grow and develop.

There is a problem, however, and it is quite simple. The problem is this: Facebook seems to have been explicitly designed to NOT be a rolodex, to NOT scale to thousands of friends per user, and to NOT be an application that scales to the needs of highly-networked businesspeople as a function of their job. I don’t think it’s just a difficult engineering problem that will be overcome with time – it’s intentional. And, more than that, I think that accounts for the success of Facebook.

Facebook’s success isn’t just dumb luck (though there was almost certainly some luck involved). There are lots of other social network sites out there – including MySpace, which is still (arguably) bigger than Facebook. Of course there’s also Friendster, Orkut, Tribe.net, and many more. I’ve been on all of these, and a whole bunch more to boot (more task-oriented sites like Flickr and Shelfari). Facebook, however, is much bigger (for me) that all of these. Why?

• Facebook has always been popular outside the tech/internet/weblogging crowd. On Orkut and the rest of them I always had the same kinds of contacts/friends. Some YULBloggers, friends who I’ve been in online communities with since the mid-90s, tech/business folks involved in other social networking or web properties, etc. My college roommate? Never. The girl I dated for a few months in twelfth grade? Never.
• In Facebook, you can’t “collect” friends very easily. This is a huge difference from almost all of the other social networking sites, which explicitly privilege friend collection.
• It’s easy to say “no” in Facebook. There isn’t even a message to the requester when someone declines a friend request. In some of the older systems, it was a big deal to not accept someone’s request – I suppose they thought that the social pressure to accept requests would grow the network faster. Without that social pressure, though, a paradoxical thing happened: even though it might have slowed the growth of the network, the whole system was non-threatening to non-professional users, who stuck around (in droves).
• In Facebook, your friends list isn’t the most prominent part of the interface as it was for almost every similar system in the past. Rather, it’s what your friends are doing that’s front-and-center. Having more or fewer friends is simply a way to have more or less “stuff” parading up the screen from hour to hour, day to day. The “social graph” isn’t fundamentally about the list of friends – the social graph is just the conduit to the real content: interaction opportunities with other people.
• There’s a cost to the user for each friend that they add. Each friend makes it that much more difficult to follow what any one friend is doing. This social cost is important, because although it puts negative pressure on the number of friends a user has in his or her list, it also helps most users to keep their friends list uncorrupted by non-friends who are simply collecting names (like they do in MySpace).

In all of these, there is a common thread: Facebook is expressly NOT there for collectors, it tries to privilege real life relationships as opposed to fleeting acquaintance. Scoble says,

[…]a “friend” in Facebook is NOT a “real friend.” (Let’s define “real friend” for now as someone who you’d invite over to your house for dinner). In social networking software a “friend” is someone you want in your social network. Period. Nothing more. The fact that people assume that you should only have “real friends” in your social network is just plain wrong.

In fact, I think that the distinction between Facebook and the other social networks – and the primary reason for the success of Facebook – is that is about “real friends” or at least is trying to be. MySpace and the rest were about collecting as many “friends” as you could. They were about the scope of the network above all things. Facebook isn’t about the network, but what the individuals in your network are doing: events they are going to, photos they are posting, games they are playing, chumps they’re biting, and all the rest.

Maybe the Facebook engineers were being honest with Scoble and it is just an engineering issue. If so, then they’d better watch it – because anything they do to remove the negative pressure against “collecting” instead of privileging the content over the network for its own sake could be Facebook’s downfall.