Paranoia is the reason all bikes weigh 25 pounds. If you have a 25-pound bike, you don't lock it at all. A 23-pound bike takes a two-pound lock. Get a 15-pound bike, and you need a big motorcycle chain and a lock as big as a road apple.
Generally on group rides (with bikes ranging way upward from my Rambouillet), we don't lock up at all. If we do, we hook together as many identical cable-combination locks as we need (all with the same combination, a date we can all remember) to go through all the frames. The locks are less than $20 at REI. By myself, I use a light Kryptonite cable, also w/combo lock. and leave the bike where I can see it. I'd rather sit with the bike than carry a heavy-ass security device.