Track Slack ???

Why do you guys who ride track put so much slack in your chain on track days? What's the theory behind running your chain so loose?  

we don't run our chain slack loose we set it according to the manufacturers specifications which is 25mm to 35mm, i set mine at 30mm & have no roblems during my last outing at the track.  

'Suspension travel'

Adjusting the chain slack a "little on the loose side" adds

some geometry...

Works well for street riding as well.  

Here's what I found somewhere else:
Chain adjustment is also critical. If the chain is too tight the shock will not be able to function correctly as the chain will limit the movement of the swing arm.

Is this right? It sounds weird to me.  

Yep, that is exactly true...think about your swingarm traveling in a circle around the pivot bolt. When the swingarm is perfectly inline with the final drive gear on the transmission, at that point your chain will be tightest. So if your chain adjustment is set to tight from spec your swingarm won't be able to travel past that horizontal part therefore limiting its travel. Whereas if it's set too loose, technically not as bad, but you risk slipping off the sprocket or losing power b/c of the excessive play.  

I'm having trouble visualizing, but I believe you.