You betcha. Hard drives fail, screen backlights prematurely fizzle out, keys pop, trackpads delaminate, mag-safe connectors melt, iSights quit working, batteries break down. These are just a few potentials that could occurr that doesn't fall under the 'accidental damage' (which AC doesn't cover) that if you did not have Apple Care and were out of warrantee, could leave you hurting.
Plus laptops go places. Some of them more hostile than others. AppleCare isn't like your garden variety warrantee that the Best Buys and Circuit City salesmen try to push on you whenever you buy a stereo or something. When you spring for the AC if something goes wrong, you need to have it fixed (like my groovy CD drive) and need to tell Apple to jump, they'll ask how high and fix it.