Do lots of people get subconjunctival hemorrhage, or is it unusual?

Somewhat common. This is a benign bleeding from a small vein in the space under the clear conjunctiva over the white of the eye. Due to oxygen exposure it stays very red until absorbed. It can spread over a broad area and look very dramatic. Usually there are no symptoms except the redness. If the vision is changed, or there is pain, see your ophthalmologist. Otherwise you can wait it out.
Very common. Subconjunctival hemorrhage is very common from simply rubbing your eyes, allergies, etc. If recurrent or severe, you need to see your eye care professional for evaluation. Especially common in folks on anti-coagulant medicines...