When it comes to other people's bikes, I do ask permission - much as I would ask for permission to pet someone's dog or cat. "May I?" My voice and my outstretched hand tremble with anticipation. The owner is amused and delighted, if somewhat taken aback by the intensity of my interest.
But though my case may be extreme, I am hardly alone in the bike-fondling affliction. Even without asking, strangers will often stroke my bikes absent-mindedly - their hands drawn to a leather saddle, a headbadge, some shellacked twine, lugwork. "This part here..." an acquaintance suddenly said mid-conversation, pointing to the top of my bike's fork. "It's so... cake-like! What is it for?" Excitedly I began to explain about fork crowns, but stopped myself as the poor person's eyes glazed over. They didn't want to know. But they did want to touch.
I think that bicycles - particularly bicycles with all sorts of interesting or organic-looking bits on them - tend to invite tactile attention. Say what you will about looks mattering or not mattering, but when a bicycle draws us in physically, surely that is a good thing.
Are you touchy-feely when it comes to bikes? Do others tend to touch your bike, and do you mind?