Do you live in an area that has them in high numbers?

Sadly not, never got to have any of those. I had black widows, but we had to buy them.

Important things are keeping your bed away from the walls, checking the blanket and pillow before you get in bed, and checking clothes and shoes before you put them on, since like you said, they can bite if trapped between something and your skin.

Yup. But if you do that (even half-assed), there is a pretty good chance you'll never ever get bitten.