The trouble is with this issue is that there can be numerous reasons why the IP address can change, most of them mentioned in the previous posts,
however as SS does have rudimentary log-in procedures in place I cannot see why SS cannot limit the number of simultaneous log-ins by the same user.
I would suggest 2 max but an admin defined amount would be better.
EG BILL logs in with lappie at work, checks library, powers up phone (different IP), downloads music for journey home.
If Bill forgets to log off from work then when he get home and logs on via home pc. SS automatically say's whey!! already logged twice so logs off Bill from work.
Now if Bill isn't the friend you thought and has shared his log-in details then when Bill(2) logs in he will log of Bill(1).
After a while they will both get very seriously p***ed off with this situation or by means of natural selection will resolve the matter so we are left with just 1 Bill
But the end result is your bandwidth is saved
