Honestly, I think that most of us here are NOT the average cyclist. We are anal beyond belief (even those of us who think we aren't). You can tell when someone is anal about their bike, and when they aren't. And you all are very anal people.
I think a few drops of lube on someone's chain is a nice thing to do (you can tell the difference between a waxed chain and a 'hasn't seen lube or cleaning solution in 9 years' chain).
Going so far as to pull a wheel to fix something might be misconstrued easily, but the end result is positive.
I occasionally fix my neighbor's bikes without their knowledge, but usually little things, like air in tires, brake toe in (to stop the squeal), lubrication, etc. They are good people, they just don't understand bikes. We sometimes ride together, and I HATE riding with people who's bikes are messed up. Going into our common basement and tweaking a few things like a lube angel late at night is the best way sometimes.
No one appreciates a favor anymore, but if they don't realize they received it, they'll still benefit, and the world will be a tiny bit better.
peace,
sam