Saying all you can eat but only for 5 minutes is a stupid analogy that describes a cap, not a throttle.
A cap means when you hit that limit you are either done or be prepared to pay with an arm and a leg.
A better analogy for Virgin is, you can drive as fast as you want, but once your gas tank is empty you have to slow down to 45mph. You can keep driving for as long as you want and as far as you want, without paying extra, but only at 45mph.
And how much data are you REALLY using?
If you use wifi while at home or in places that support it, very few people will actually even hit that limit. Very few people hit that limit without any effort at all. Even after hitting the limit you still have plenty of speed for music streaming. Web surfing may be slowed a little, but considering most peoples speeds before the limit, it will hardly be noticeable.