At a bus stop, yeah, it is kinda strange, cause people are usually there because they have to be, not because they want to. At a hackerspace, at a bar, at a book club, music concert, etc. it isn’t weird all. Some of the best friends I’ve made over the past couple of years (and i mean real friends, the ones you hang out with multiple times a week, go on trips, etc), it almost always was through some kind of spontaneous contact. I guess it depends on where you live. I’ve found (anecdotal evidence incoming) that it is much easier to do so in big cities with a lot of people that are not car-centric.