Are 2GB of mem even necessary for a notebook?

Intel Core Duo L2400 (1.66 GHz) Processor
100 GB 7200 RPM HD
etc., etc., etc.

In what kinds of circumstances would notebook users even need
2GB's of memory? Just curious.

Oh, and I actually had a question which sort of relates to this...
Anyone know what kind of performance gain to expect between a 5400RPM hard drive and a 7200RPM hard drive? The 5400rpm will run cooler, but is a 7200rpm hd worth the couple extra hundred bucks (in terms of performance gained per dollar say)?