@dsuke
Actually, primae noctis right isn't the right of the landlord, it's the right of the peasant and religious duty of the lord.
Defloration ritual is an ancient tradition that comes all the way from the ancient Sumer, long before the Bronze Age collapse. Back then, the virginal blood was considered a curse, just like the menstrual blood, because the latter often lead to the inflammation of the penis in case of sex during a woman's period (for obvious reasons). Therefore, the defloration was conducted by the head priest of the city-state, because his mandate to rule the city-state stemmed from the divine marriage with a patron god and therefore any sexually-transmitted curse on him was purified during the consummation of such marriage.
And since the whole concept of divine mandate never left the feudal system, early feudal lords had the same divine authority as a head priest of a city-state, if only for this particular tradition. That is exactly why there were versions of this ritual where the landlord had to step over the newlyweds' bed, for example.
I hope, this rant about religious significance of what is being widely misinterpreted as corruption and slavery was interesting at least a bit.