too much stuff, all over the bike, depending on where/how far. Most of my bikes have a wedge bag with the basics- tube, patch kit and levers, small multi bike tool, and some duct tape. Pump, of course. Maybe some zip ties, a couple of spare brazeon bolts, some bailing wire, a prestsa/schrader adaptor. All the other stuff like ID, cash, key is a given.
I started outfitting each bike with its own seat bag and kit because I didn't like the hassle of moving the repair kit, pump, etc, and making sure I had the right diameter inner tubes....one time I flatted on a my 26" cruiser, went into the seat bag to grab the spare, and it was a 700c.
All the rest of that crab, well, I guess if it makes you feel better out there, haul it around. I've never heard of anyone losing a seatpost clamp. Maybe it happens.