thinking aloud here, but...
even though root maybe easily hacked (i'm not aware that i have to enter any password when typing root ?!?) doesn't the very fact that we have a very small user base protect us against "hackers"?
it's fun to hack on our beloved N900s, but what "crook" would be interested in it?

for the applications running in user space, in how far would putting our data under root:root (i think) protect it from casual app access?

final thought about spying apps... doesn't the limited mem & cpu resources protect us against the worst of those in that an app / deamon / whatever that would intercept kbd / sound / touch / display would practically bring the N900 to a standstill?