I always get aggressive when people touch the screen of my 770 with their fingers instead of the stylus. i'm tired of cleaning it all the time - nothing leaves more dirt on such a surface than fingertips.

also, a "finger-driven" user interface wastes precious space... you simply need larger controls for fingers. see the size of the full screen keyboard and compare it to the normal keyboard for use with the stylus. I wouldn't want a whole device crippled by thumb-sized controls.