You all R right
some p2p clients and worms can destroy all network traffic.
There is a couple of methods to find "bad client", but in some cases it could 
be very difficult (for example if we have WLAN broadcast network [some 
access points] ) behind LAN Interface.  
By reducing max number of sessions to single IP or group of IPs we can safe 
WAN traffic and router utilization. 
So, the point is how to limit max number of sessions, NOT how to find  "bad" 
clients or how to enralge number of NAT translations on router.

Thought for the day:
    Dictatorship (n): a form of government under which everything 
    which is not prohibited is compulsory.