My children are grown--early twenties. We had one wild and crazy teenager and one sedate teenager. We kept the computer in the family room/kitchen area. No computers in their rooms/No TV in their rooms. They did have phones in their rooms.
The wild and crazy teen is now a responsible adult. She recently commented that, when she has children, they, too, will have no computers/no TVs in their rooms. ALSO, she says they will have no phones in their rooms. Interestingly, she says that, if she has several children, the boys will be in one big room and the girls in another big room. She thinks she had too much alone time due to having her own room growing up. She thinks kids would do better sharing bedrooms. She also would like a central, large play/hobby room so that the bedrooms are strictly for sleeping/dressing.
The matter of trusting kids is delicate. I ultimately decided that, as long as they gave me no reason to doubt them, I respected their privacy. As soon as the nutty stuff started, the trust was broken; and I got nosey. So, one kid got her room, book bag, purse, etc. thoroughly checked out (on the sly) rather routinely, and the other one didn't. I did, however, check the history for both kids on the computer--less often for the sedate kid than the wild and crazy one.