LOTS. I do not know exactly but lots and lots....If there weren't many then orthodontists wouldn't be so busy!
Almost everyone. It's a matter of degree. Most people have at least one tooth not perfectly aligned. About half the population have many malaligned teeth. It's not uncommon. If you have concerns, see an orthodontist for advice.
Crooked teeth. Almost everyone has crooked teeth on some level. It may be 1 mm to something much more substantial like 12 mm of crowding.