ISPs implementing bandwidth caps is something that has waxed and waned since the first days of the Internet, and is something that is coming back into focus as they look for ways to solve the issue of ever-increasing bandwidth demands. Comcast, for instance, has toyed with the idea of a 250GB monthly cap, something that on the surface seems reasonable.
Other ISPs are looking to be a little more draconian. One ISP in the U.S., for instance, apparently has decided that a mere 5GB of traffic is too much and can warrant termination. Only 5GB? Even though the ISP claims that they will not be terminating anyone who exceeds that, they are certainly making it clear that they see 5GB as excessive - and could decide to terminate if they saw it fit.
Were this 1997 and broadband a rare thing with Internet backbones in their infancy, I might understand. But today, when a few hours of streaming from Netflix or a few days of YouTube can burn that much data, it seems many ISPs have lost touch with reality on what constitutes "excessive" consumption. An interesting report based on documents uncovered from an ISP indicate that a lot of the bandwidth caps are being put in place to increase profit, not to combat a saturated network - which could easily leave a bad taste in the mouths of customers should they find out. While a bandwidth cap is something that is understandable, there is definitely a point where you leave the realm of providing "acceptable service" and simply start ripping off your customers.