Virgin Media are implementing Subscriber Traffic Management on their broadband service. This applies to all their services, but I'm only concerned with the XL cable offering:
Between 4pm and midnight, bandwidth monitoring is enabled. When bandwidth monitoring is enabled, if you download more than 3GB (which can take less than 30 minutes), your speeds will be throttled. Normal speed is 20Mb down/768kb up, throttled speed is 5Mb down/256kb up. The throttling will last for four hours, after which the bandwidth counter will be reset.
Now, if you take the time to think about this it's actually a very nice form of throttling. You still get usage of the connection at a reasonable speed and it only lasts for a short period of time. It's also explained fully up-front - there's no playing "guess what the cap is". And also note that there is no per-protocol traffic shaping. I've seen much worse (Demon Internet for one - if you download more than 50GB in 30 days you get ISDN speeds for a month).
So why are people up in arms about it? Case in point - one poster got throttled after 6 hours (turning his 4Mb service into 2Mb). His bandwidth usage was around 1Mb, so in practice he's not actually affected by the throttling. Yet he's complaining that he's "convicted and punished as a heavy user just [for] playing a poxy game", and then flames anyone who points out that his experience isn't actually suffering.