I'm surprised how many of DDs' friends text really late at night or put stuff on facebook at 11, 12pm even later, and this is on school nights, I'm not fussed about weekends.
My DDs say that all their friends don't have a controlling mother like me who makes them leave their electronic stuff downstairs at night. But they're 12, not 16, they're growing madly, and need their sleep.
My 12 yr old's phone is with her, but she rarely sends texts as she's on PAYG. Her computer is also in her room, but the rule is it's off when she goes to bed (same for her phone). She manages to stick to the rule, so I don't take them off her.