The national electric code does not (generally) restrict the number of electrical receptacles that can be put on a single breaker. This is because the breaker is designed to protect the cabling. No matter how much you plug into those receptacles, the breaker will prevent you from overloading the wire. In a typical home, most are either unused or serving loads with negligible or very low current draw. (DVD players and TVs don't draw all that much. Clock radios draw practically nothing at all.) The largest cord & plug current loads in a house are things like coffee pots, hair dryers, curling irons, space heaters, microwaves- basically things designed to heat up as quickly as possible. With the exception of space heaters, most of these are on for very little. And kitchens and bathrooms- the location of most of the high-current appliances- DO have special restrictions on receptacles.
Appliances are designed and tested for power consumption. They are designed to never draw more than 15A, which is the maximum design current for a typical 3-prong plug, which is what protects the plug from overloading- even if there is a 20A breaker, that coffee pot or hair dryer will never draw more than 15A. This is all fine and good until the homeowner plugs in a 10A extension cord with a splitter and plugs several "15A" plugs into it, defeating the deliberate rating and testing process. (This is why power strips are so frowned upon, even if they do have that worthless little 15A breaker.)
The electrical code prohibits "permanant" extension cords because they present a much higher risk of fire than permanant electrical cabling, as they're more exposed to damage. The national fire protection association doesn't care that you have your lamp further away from the outlet than the cord will reach- they just would rather you have a safe place to plug it in.
