>affect the switch performance
Heavy flows can affect switch performance. For example, if you have a 1Gb/s multicast flow coming into a port on a 48-port switch where the other 47 ports are a member - it would have to duplicate that packet 47 times - producing 47 Gb/s of bandwidth.
Back in Cisco Enterprise land, I have had this problem with companies that use lots of multicast (usually for media) and I have had to put in higher-end switches to cope with those flows.
If your flows are small, you have nothing to worry about.
