When you switch a classic IBM PC compatible personal computer, what happens? It tries to boot. In other words, it goes hunting for something that it can surrender itself to, something it can become. Armed with a boot device a PC ceases to be a PC and becomes something else. Common examples are Microsoft Windows PC's and Ubuntu Linux PC's. Less common examples are QNX PC's and Plan 9 PCs.
For many many years now, we have become accustomed to the notion of booting as something that hard disks are involved in. Inside your PC is a lump of spinning magnetics that the PC BIOS goes hunting for to boot - unless you are setting up the PC for the first time in which case you boot from something else, like the CD-ROM drive. I remember booting my first PC from a floppy drive because that it all it had to boot from. It wasn't pretty. What was pretty was the fact that the PC has always had this ability to hunt around for things to boot from in sequence. At first it was floppy drives and then hard disks. These days it is CD-ROM drives and then hard disks.
The easy swappability of bootable PC CD-ROM disks has been put to great use in the form of the live CD. With Live CDs like Ubuntu or Knoppix. The intriguing thing about these is that they do not change your PC in any way. They simple take it over for a while. When you reboot having removed the Live CD, the PC will revert to whatever it was before - generally whatever operating system is installed on the hard disk.
That is pretty interesting I think. What if the thing you booted from was not a read-only medium? What if it was something like a USB disk? With such a set up you could carry your entire world around in your pocket - operating system, applications, data, the lot - pop in into any host PC and boot your world.
What is wrong with that picture? Well, at a hardware/software level, machines that can boot from USB devices are relatively new phenomenon. At a business model level, well, its a bit of a game changer potentially. Imagine a world where it is drop-dead easy to boot from a gadget you stick into the side of a PC - perhaps USB, perhaps eSATA. What would be the implications of such a thing? I could imagine myself having umpteen different PC's - one in each pocket - and booting them as required. I could imagine sliding up to a PC host on an aeroplane or in an office reception area and booting my world. I could imagine checking into a hotel and booting my world on the PC build in to the TV in the room.
I see no technical reason why this cannot happen. The range of things that your average PC can boot from keeps growing. Moreover, the once dominant hard disk is beginning to look like it is heading the way of the floppy disk as users and hardware manufactures throng to the promised land of solid state device trickery. Why insist that the only solid state gadget worth of booting from is buried inside the casing of the PC itself?
How long, do you think, before it is commonplace to boot a PC by connecting your phone into its USB/eSATA/some-other-drive-interface port?
Not long at this rate.