How to use Time Machine with a laptop?

Time Machine seems great to me. I already set it up at home, and it's working fine. But now, the big question... What about laptops? I mean, I use my MacBook during the day away from home (I'm not carrying a FW HD everywhere I go, right)... Didn't Apple thought about this?
Isn't there a way to back up through the internet? C'mon, I have a .Mac account, I can now access my home mac from anywhere... Is this be so hard to do?

Hope I'm deeply wrong, and there's a solution for it...