Once the idea of an operating system being independent of the hardware took hold in the PC market several things happened; hardware became less important to your average buyer, as long as a computer ran Windows you knew where you were, this led to people losing brand loyalty to the hardware brands.

The newly levelled playing field meant that hardware manufacturers were no longer dependent on relationships with the brand owners and could sell their hardware to anyone and suddenly assembling and selling a working computer from off the shelf parts and software became relatively easy. This pushed prices down and helped the PC become a household item, and every new PC came with Windows.

This is what is now happening with Android, while Apple and RIM stick to the proprietary hardware/software combo, Google have made an operating system that anyone can use. Companies that have the hardware capabilities to produce smartphones no longer need to partner up with a big name or develop their own operating system and UI to get in to the game. HTC for example have gone from relative obscurity a couple of years ago to a major player in a relatively short time, all on the back of a few Android phones.