Twitter – Good and Bad

fractal by kevindooley
Am I Done with Facebook? Twitter FTW!:
[Via Phil Windley’s Technometria]

I got a message from Facebook today saying that someone had friended me. I realized I didn’t care. Not that I didn’t care about the person who’d friended me–I didn’t care about Facebook. It’s been weeks since I was there and my life is pretty much the same.
I think the reason is Twitter. Twitter is much more social, much more interesting, and the plethora of clients (including any mobile phone with SMS) means that I don’t have to remember to go check the site to see what’s happening. Twitterific displays a solid stream of the 140 character thoughts of my friends.

Because of Twitter, today I know:
There were tornados in Denver and Laramie
Twitter posted an article about their architecture on their blog
There’s a blogger dinner tonight in Salt Lake City
@tylerwhitaker and @bradbaldwin aren’t going to carpool to the blogger dinner

I like that.

Twitter has scaling problems even though their user base is reportedly quite small. As Nik Cubrilovic points out, Twitter isn’t like WordPress or Digg. Twitter is a group forming network (GFN). When a Metcalfeian network adds another user, the number of potential connections goes from N2 to (N+1)2. When a GFN adds one more user, the number of potential connections goes from 2N to 2(N+1). In case it’s been a while since you’d done that math–it’s a big difference.

There are three important ‘Laws’ dealing with networks, social or otherwise: Sarnoff’s, Metcalfe’s and Reed’s. Sarnoff’s Law states that the value of a network (David Sarnoff started NBC) is proportional to the number of nodes. Metcalfe’s Law states that the value of a network is proportional to the square of the number of nodes. Reed’s Law states that the value of a network increases exponentially with the number of nodes.

Sarnoff’s is linear. It simply demonstrates how much NBC would make if another viewer joined the network. Since the network communicates in only one direction from a single source, the number of connections does not change much with increasing numbers of nodes.

Metcalf’s assumes the nodes can communicate with each other, resulting in multiple connections. This is where network effects come into play. One phone is not useful. Two are a little better, but a network of 10 can be very useful. Metcalf first showed this using this figure:


The line corresponds to Sarnoff’s Law. Metcalf’s, which was derived from the first Ethernet networks, shows that the value for small numbers in a communication network is not great. But this increases rapidly with larger networks.

Now Reed’s law looks at the number of groups that can be formed in a network. So take all the nodes 2 at a time, 3 at a time and so on. This results in the number growing at a rate proportional to 2N. This is much faster growth than Metcalf’s. You can be a member of several different groups, some which have members in common and some that do not.

What this means is that in some social media settings, the number of groups can increase much faster than the number of connections. Here is a consequence of this:

To make this more real, consider TechCrunch’s twitter account. When TechCrunch, with almost 18000 followers, sends a message, that results in 18000 messages–one to each follower. This is like the phone system with infinite, always-on conference call capability. Sure, you can do things internally to collapse some messages, but you’re still dealing with exponential growth.

What is happening with Twitter, that is making it have problems scaling, is that the number of groups substantially increases the number of possible connections and messages it might have to maintain. With email, everyone on the list is sent a copy of the email, that sits on their computer and take up space. Twitter sends messages to phones, for example, possibly 18000 of them in this example.

That is a lot of wasted effort. Twitter may not be the best way to communicate with a large number of people in several different groups.

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