We're talking vanilla warband here, right? If you get power throw of 5+ you can generally take out swadian knights/huscarls with a single throwing spear.
Keep in mind that throwing axes do cutting damage, not piercing or blunt damage, so heavy armor is liable to reduce much of the potential damage that throwing axes will do. Throwing axe will do bonus damage to opponents with less armor.
Would be cool if throwing axes would bounce/ricochet, though. Wish they'd do that for M&B 2.
It was sort of was the point of carrying throwing axes instead of javelins, they tend to bounce off of hard objects and continue onwards.