It is not a matter of fragmentation, it is a matter of what the fragmentation does. Apple as one device, Nokia has 100? Android also "has" 100 devices. Fragmentation on iOS is not possible. If you try to defragment Android, you will end up with lots of equal looking devices. Good for Google, but bad for everyone else. Nokia on the other hand, can do whatever they want with Symbian and MeeGo, it will still be Nokia, and look Nokia. MeeGo will be fragmented to pieces, but still share a common ground, the kernel.