From another point of view I always marvel at riders who appear to carry nothing more than a cell phone.
You see them with a tiny underseat bag big enough for said cell phone and a bit of cash, look at their pockets and see an Ipod bulge, no pump on the bike, no tools and you wonder. Are they incredibly lucky, never go on 80mi jaunts, just riding the hood? After two experiences with triple flats on centuries, I never have less than two spare tubes, a patch kit, a tire boot (tevdek) and a multitool, (never used so far), plus pump which add 15-18oz to the ride load, plus a couple of snicker bars and or gel packs. Probably overkill and I have thought about the recent spate of 16# bikes and what it would be like to ride something less than 24#...
Steve