Actually...
1) The acceleration needed to remain on the surface in spite of the earth's rotation at the equator would amount to about 0.037 m/s^2 or 0.004g according to quick and possibly incorrect calculations (a=v^2/r, d=14*10^6 m, feel free to doublecheck) so there IS a difference albeit very much a negligible one, especially as the gravitational constant varies approximately between 9.80 to 9.82 depending on latitude anyway IIRC.
2) The gravitational force is inversely proportional to the square of the distance. F~1/r^2.
3) Mass remains constant (except in nuclear reactions). Weight is the force the scale measures and changes with the gravitational constant etc.
Cheers,
/ft, certified nitpicker
(Edited to make sense)
[ 16 August 2001: Message edited by: ft ]