Why do rabbits wiggle their noses?

From: http://bunniez.hubpages.com/hub/Why-Do-Rabbits-Noses-Twitch

"Experts believe that rabbits twitch their noses because twitching moves about the sensitive smelling organs in their noses and exposes them to more air. This means that they are more likely to smell a scent, even if there is very little of it in the air."

If the amount of twitching seems to correlate with the amount of focus (are they afraid of something and trying to get more info? is there food coming?) the rabbit has. As your rabbit gets use to you, it should become more relaxed around you and thus nose twitches should happen with less frequency.