Lending/sharing, persistence (particularly against accidental or intentional deletion), device-independent access, resale, marginalia / underlining / dog-earing / highlighting, proven archival format, physical mnemonic value (there's something about the reading pile by the side of the bed or book left for a quick 1-2 page read in the bathroom), freedom from DRM.

Electronic media offer benefits as well: searchability, ease of duplication, amenability to quantitative/qualitative analysis (one example: http://www.ted.com/talks/what_we_learned_from_5_million_book...), extremely compact storage.

Both formats have their benefits. I'd greatly dislike having hardcopy disappear entirely. I appreciate the utility of online media.

The biggest concern I have with the Amazonization of the book industry is that we're moving from a highly concentrated publisher-dominated model to an absolute monopoly at the retail/distributor point. I'm very, very leery of concentrations of control and influence.