iMessage is one of the best features Apple introduced on WWDC. Especially since it makes iOS more valuable. It makes it more valuable since it is:

• An extra feature which most people are already using via another provider (ping, whatsapp) or via a paid version (SMS). It will save money for quite some people.
• It becomes more valuable over time if more people use it. The basis of iMessage is using the network of iOS users.

That is a real network effect: the platform becomes more valuable over time as more people join and start using it. iOS did already become more valuable over time as more apps were created by other people for the platform. Now it is not only app ecosystem, it is now about you and your content. The more friends you have with an iOS (5) device, the more valuable iMessage will be for you but also for your friends.

Peer Pressure and network effects

If all your friends are on iOS and messaging / texting each other (take into account that teens send around 3300 messages per month) you are likely to switch to iOS as well. Since you want to text for free and you don’t want your friends to be paying for the texts they have to send to you. This is also a bit of peer pressure, since you might not be able to be part of a group if you are ‘difficult’ to reach (or if you are ‘costly’).

Even though Ping might have been a move from Apple to building a social platform, iMessage might be the thing that really succeeds. Not in creating a big social network, but by creating multiple small world networks. Foremost the use of the network effect and introducing a bit peer pressure to make people switch  (you don’t want your friends to pay for texting you, so you’ll switch to iOS if almost all your friends are using it) might be boosting apple’s markets are even more and at the same time makes switching even harder since leaving a social network is always hard since you are invested in way or the other.