Cam Lean is just what it sounds like...your cam actually leans to one side or the other at full draw. It can be caused by improper cable or yoke adjustment, a weak cable or yoke, or a worn cam/cam bearing or axle. It can also be from a weak limb. Most often it is too much tension on one side of a cable or yoke that is actually causing the limb to twist.

Given the why you can see it would be more likely to occur on a twin cam system. Also the larger and more agressive the cam the more likely to get lean.

Single cams are not immune to the issue but it isn't found as often.