It will really depend on what you are polling. If you are polling a router with a few interfaces, you'll have a certain amount of bandwidth. If you're polling all ports on a bunch of switches, you'll use much more bandwidth. People have noticed on our netflow graph that one of the top 10 endpoints is almost always our secondary poller for one of our sites. They ask why it does so much data and I tell them it is because it is polling all the devices at the other end. (Probably about 100-200 devices many of which are swtiches.) They asked if I could reduce the amount of data and I told them I could no monitor all the switch interfaces. It all comes down to what kind of data you want to see.