It's a handheld computer. You can certainly argue against having the right to customize it, but there is no technical reason you shouldn't be able to. It's not a toaster.

Hey now ... that's not fair to us toaster hacking people ... we too like to enjoy our modified toasters.

http://www.embeddedarm.com/software/arm-netbsd-toaster.php

I hacked my dinosaur toaster so it toasts a picture of RMS. it's awesome.

You can customise it, just not arbitrarily.

I can change the display format for the time in the status bar, but I can't have an animated kitty running about up there, as much as I'd like to.

Reminds me of a tiny thing on my jailbroken device that pleases me: http://i.imgur.com/1QXUm.png - every slider is an animated kitty. (It's called NyanSliders in Cydia, in case anybody else would like it, and I think there's an unrelated version of the same concept available for Windows too.)

Don't toasters have computers in them now? If they don't, they soon will.