SPANning ports on Cisco Nexus 5K Switch "brings down network"

DO NOT SPAN PORTS ON NEXUS 5K

Cisco Nexus 5000 Series NX-OS System Management Configuration Guide, Release 5.1(3)N1(1) - Configuring SPAN  [Cisco Nexus 5000 Series Switches] - Cisco Systems: If a destination port is oversubscribed, it can become congested. This congestion can affect traffic forwarding on one or more of the source ports.

I'm told this is not an issue on 7K's.