In fact, we know that ISPs are taking advantage of this situation: Witness the FCC's ongoing interrogation of Comcast regarding its network management practices.
Think this is only a problem for BitTorrent users? Think again. This time around, the FCC is looking into Comcast's boasts that its VoIP service is more reliable than competitors' services during high-traffic periods.
Sure, any company that buys its net bandwidth from the cable guy is nursing a mile-wide masochistic streak. The point, however, is that very few small businesses have an easy, effective way to know whether an ISP is playing them -- and their VoIP providers -- as second-class customers.
M-Lab is still in its infancy, but it already provides a suite of three free online tools that test broadband connection speeds and diagnose common connectivity issues. Better yet, M-Lab will soon launch additional tools that can tell whether an ISP is giving some types of traffic (such as VoIP) a lower priority than other traffic; and indicate whether an ISP is degrading the performance of certain users, applications, or destinations.
M-Labs' technology is still very much a work in progress. As open-source projects, however, they are free to use -- and for others to improve. Given the ferocity of the net neutrality debate, you can bet this is one open-source effort that won't die on the vine for lack of developer interest.
Full disclosure: I am an ardent supporter of net neutrality, including net neutrality legislation. But the M-Labs initiative isn't about politics or policy; it's about accountability. ISPs should tell paying customers exactly when, how, and why they "shape" the Internet traffic that moves across their networks.
And those ISPs should face the consequences if customers catch them saying one thing but delivering another.