Well there's several ways to do multi-touch (only one is possible on the N900 though if ever implemented). It was done on the n800 too.

- real resistive multi-touch requires a certain kind of resistive touchscreen. Technology that wasn't readily available when the N900 was first planned and being produced.

- pseudo multi-touch using a combination of hardware (like proximity sensor and touch screen) or having the system remember where the screen was first pressed and then apply that with the second. I believe the second has been done on the n800 and maybe the N900.