Originally Posted by richardmasoner
Those are fixie skid wear patterns. You're supposed to rotate your tire every once in a while by removing the chain, turn it a fractional rotation and remount the chain to even out the wear.
Some gear ratios are more prone to this than others. Check out:
http://sheldonbrown.com/gloss_sa-o.html#skidpatch
Sheldon "High Denominator" Brown