Question: When working with electronics, it is quite easy to regulate current with a resistor, potentiometer, switcher, etc.

But take a simple high power application such as an electric stove. What method is used to control the current through the burners. They couldn't possibly use a variable resistor because the heat generated would be on par with the burner. 

It is clear however that the controls are disipating very little heat and they certainly aren't using any electronic devices. So how do they do it?

Answer: 
simple electric ovens use simple temperature control usually using something like a bimetallic strip (you can here them click in and out) where the dial is used to set the point of electrical contact that will then provide electrical power to the heating elements.

the result is more of a hysteric control with a very long duty cycle (where the duty is governed by the thermal characteristics of the oven - ie how long to cool) and the lower band to-do with specific characteristics of the thermistor/bimetalic strip.

More modern electronic controllers do a similar thing but use thermalcouples/RTD to measure the temp and then semiconductors to switch the power (SCR's)
[Pulse-width modulation (PWM)](http://en.wikipedia.org/wiki/Pulse-width_modulation) switching allows to reduce losses in the control circuitry. The switch element (transistor, thyristor, and such) is either

* Fully on. Large current is flowing. The voltage drop across across the switch is low. Power loss on the switching element Ploss=IswVsw is low, because Vsw is low.
* Fully off. No current is flowing. The voltage drop across across the switch is equal to the supply voltage. Ploss=IswVsw is zero, because Isw=0
* Importantly, the switch can be in transition from on to off. But, this transition is fast, and only small amount of energy is burnt by the switch element during transition.

PWM (or variants thereof) is a very common technique.