This really looks like the future to me: no need to own a physical machine, but instead multiple virtual machine you can get access to from anywhere.
Join and use your personal workstation from the airport, from an Internet café or from wherever you want! No need to reinstall or setup everything each time you arrive somewhere. Access your office machine right from your laptop through a wireless connection.
Soon, you'll have a virtual machine for working, one for gaming, one with VS200X, one with SQL Server 200Y, and they can be active at the same time and see each other. Preconfigured virtual machines will be available and you'll just have to make a copy to start using them. Backups turn easy: just archive copies of the virtual machines.
Not a lot is missing to get to this picture. Just a little bit of bandwidth maybe?
How does this sound? Will we see a new business soon: virtual machine hoster?
Update: As Eric suggests in a comment, we may indeed carry virtual machines around on USB keys or portable music players.