Floyd and Fall's "Promoting the Use of End-to-End Congestion Control in the Internet" discusses the problems caused by flows that are not regulated by congestion control and that are not TCP-friendly. It also shows how such flows can be controlled. That is, routers can examine traffic and determine if there is a TCP-unfriendly flow, then refuse to route the flow's packets.
A search using Google Scholar shows that over 1700 publications have referenced this article. It is reasonable to assume that ISPs are aware of techniques to block greedy flows. If these techniques are used today, I imagine that most traffic regulation would be done at the edge networks, rather than at the core of the Internet. The overhead from examining a flow's traffic scales as more flows occupy the same router.
It is known that ISPs throttle certain types of traffic, but not all of their policies are advertised. Knowing policies influences how applications are engineered. For example, ISP-friendly versions of BitTorrent have been made that make both ISPs and end-users happy. The more we know about ISP policies, the more we are able to make applications that are ISP-friendly, and that also work well for end users.
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