Frame Rate

I have worked with Flash for a few years, but only recently have I given much thought to frame rate.

What is a common/recommended frame rate for a typical flash site? Obviously the default FPS is 12, and I have recently been creating websites around 25 FPS.

Also, what kind of processing or memory strain is a higher frame rate placing on the user? Am I making any considerable difference in file size, etc. by going from 25 FPS to…say…75 FPS?

Any information related to these topics would be appreciate. Thanks.