I've heard that the baby favours the same breast as the hand you write with... ie your dominant arm because it feels stronger/more secure.... also i suspect that your circulation is slightly greater/faster on that side of the body meaning milk is made faster? who knows why they favour.... maybe we could ask a child who has been breast fed until their "milk teeth" fell out (apparently this is a theory as to how old the human child is meant to be breast fed for according to mother nature)...and they could tell us why they have a preference!
That makes sense really and yes, I'm right handed! There was a link to a video on BB recently, posted by JustMe, and it was of a mother in the UK who is still BF her 7 year old (may have been 8 year old). I'm not sure how old the footage is but maybe she has a forum or website (given it's so unusual in the western world) and we could email her. The footage was quite amazing and both daughters (I think the younger one self weaned at 5) said how wonderful it tasted, "much better than melons" was the words one used for memory.

Hmmm, might google her!

ETA: found the footage again and apparently it's from a 2006 documentary called Extroadinary Breastfeeding http://vodpod.com/watch/932467-breastfeeding-at-8-