Should teenage drivers be limited to carrying only a set number of other teens at once?   stance: yes, teens should be limited to carrying a small number of teen passangers at once.:
Perhaps not all teens; there is a good case for new drivers. Perhaps in the first six months after passing the test, as well as provisional licensees (I think there are restrictions on this anyway) should have restrictions on the number of passengers.
Personally, I would also sugest a restriction on how far a newly licesnsed driver can travel on thier own, or with them as the sole driver. Obviously this would be very hard to police, but would prevent thousands of dangerous accidents every year from new drivers on thier first motorway jaunt.