We've told the kids they'd probably have their own laptops when they hit about 15 - about the age they'd be able to start taking classes at the local community college. (It's also when we told them they'd have their own cell phones.

). We are not big on them having that much access to information this young; and being rather eclectic hs'ers, there's not a huge need for them to be on a computer right now.
We have a family desktop ("my" computer), and a family laptop ("dh's" computer) that the boys use with permission. They are used/kept in public areas of the house and used with supervision. We don't like the idea of computers (or TVs for that matter) in their rooms, and purposely plan to keep those types of items in public areas of the house.