I have a theory on this.

Plateaus occur naturally and may differ from person to person, but they are cyclical. If you chart your progress, you will notice these cycles. Mine are aproximately 2-3 weeks, every 3 months or so. Some may never experience them, but most people do.

Stalls occure due to physical reasons, slowing or stopping your weight-loss. Examples are: taking certain drugs and medications, starvation-mode due to under-eating and muscle-loss, yo-yo dieting.

Pseudo-stalls or "fake" stalls occur when people just consider their weight on the scale, and not pay attention to their measurements, and fat to muscles ration. A person who think they are stalled in such a case may try to change their diet, while in fact they are changing what is working for them and try yo-yo dieting again and/or undereating. Most common reason is expecting fast results, these expectations are simply due to comparison with other people's rate of loss and/or TV commercials.

Wa'il