2 GB will be horrible even for just Safari. I would feel sorry for you if you have 2 GB.
2 GB if you're just planning on typing with TextEdit all day,
4 GB should be enough for Safari,
6 GB for Keynote, Pages and Numbers.
8 GB for Gamers, Photoshop, Indesign, Aperture, Lightroom and rare AE projects
10 GB for very short (3 minute) Final Cut Pro X projects,
12 GB for rare 12 minute FCPX projects, and a bit more common AE projects
14 GB for insane Photoshopping (500 layers on 4096x2000 at 300 DPI), and common 12 minute FCPX Projects,
16 GB for frequent AE projects, 20 minute FCPX Projects,
32 GB for 10 Motion projects rendering while 30 minute FCPX is rendering and an AE project,
64 GB for 50 minute FCPX project with few effects,
128 GB for 50 minute FCPX projects with a lot of effects,
256 GB for 1.5 hours of FCPX projects with few effects,
512 GB if you're making a harry potter film.