There are some things that don't happen much in cars, especially when commuting. When every other car is seen as an adversary (and I've had days like that myself) being sociable with your fellow travellers is one.
However bikes are different, certainly folding bikes at least it seems. I had to wait to cross a busy main road just now on the way home. As I pulled up to the traffic lights, there was a gentleman already waiting on a folding bike. Closer inspection revealed it to be a Raleigh Stowaway in very good condition indeed. I commented on the fact that it could be considered a classic and a good conversation about folding bikes began. Turns out that this chap owns a few of them. Anyway we ended up riding the same way for the next half mile or so and carried on our conversation as we rode.
OK so only a short chat with a stranger - not like I have a new best friend or anything. However, these things seem to happen when you're on a bike. Several people have stopped to ask me about my bike when at railway stations. No one has ever done that about my car!
I guess it's just nice when commuting can be about fun and conversation and not trying to beat the car in front across the next gridlocked roundabout.
And I should review my previously blinkered opinion about what cyclists are like to each other!