Well, it's a bit complicated and needs some software development to do well. The best way to fund a complex project would be to raise the money using an assurance contr.... oh wait ;)

 

It could be automatic in the sense that users don't need to know it's happening, but look at it this way. Gavin believes the future of computing is mobile and tablets. I don't know about that, but let's assume for the sake of argument he turns out to be right. These devices are expected to have much longer battery life than laptops. Apps that spin up in the background and use battery+radio can easily be seen as "abusive" by end users. In fact, if you look in the Bitcoin Wallet section of the forum, you'll see a giant argument by users of the Android app who are upset because the app sometimes runs in the background just to keep up with the chain! That's not even donating resources, it's just trying to ensure it doesn't fall behind, and this enrages some users because it can have a small but non-zero battery/bandwidth usage impact.

Given the number of complaints generated by just having the app sync automatically, imagine what would happen if we started relaying blocks!

Generally the ethos and modus operandi of desktops is different to laptops which is in turn different to mobiles/tablets. Things you can get away with on more powerful machines that expect to be plugged in all the time are verboten on more modern devices.

Now that said, I can easily see Bitcoin enthusiasts buying some kind of cheap embedded device, maybe Raspberry Pi based, and plugging it into a wall in order to donate to the network. That way it doesn't affect their primary devices responsiveness or storage or battery life.