And this is one reason why caped internet plans are actually in the customers interest. If you use more, you pay more, so it's in the interest of the ISP to keep you downloading stuff as fast as humanly possible.
The only time they do throttle you is when you hit your monthly quote. Then they "shape" (throttle) your connection to entice you to upgrade your plan to something more suited to your usage requirements. At which point, you click the "upgrade plan" button and you're back up to speed.
Sure, Unlimited internet is all good in fantasy land, but I really can't see how it's a sustainable business model unless you're paying for a business-grade connection on a megabit per second basis.