I realise that during the lightsaber fight scenes, you hear the cackle of the lightsabers hitting, but you don't actually see then connect :S
And if you haven't realised, the Sith people all have yellow eyes appearing at random times.
So from my powers of inference, I deduce that this could possibly be one of the ways the Sith community tries to get people to join their side.
*Due to limited stocks, we are only allowed to give one set per person.* (explaining why the yellow eyes don't appear all the time)
Disclaimer: Pretty princess girlfriends may leave you due to your demise.