do you run with a chain guard?

[mtc]

is it needed of you have a clean chain?

[T Legg]

Yes it's a safety device to keep your clothing from getting caught in the chain not to keep it from slinging grease.

[Millietant]

Your bike will fail it's annual Govt safety check here if it doesn't have a chain guard of some type - although the ones on bikes generally only cover the top run of the chain, leaving another real risk point, the nip point, on the bottom run where the chain meets the sprocket, unguarded. Covering the top run will prevent clothing etc, as has been said, being dragged into the countershaft sprocket.

Off road bikes generally have a protector on the bottom nip point that stops things knocking the chain off-line, or getting wedged between the chain and sprocket at that point (twigs, stones etc) - road bikes don't.

[Motofun]

I run a shark guard on my race bikes.  It bolts to the bottom on swing arm and looks like , well, a shark fin.  The purpose is to keep your foot or other body parts out of the rear sprocket in a crash.  I've seen the results of this type of accident and it's not pretty. In one of my crashes I ended up hugging the rear tire with the sprocket right there...I've seen plenty of bikes that don't run a front sprocket cover.  While this sprocket is inside the frame and therefore more remote, it still poses the same risk should you or a body part like a finger get in there.  I recommend using all the covers/guards.

[Millietant]

Yep, fingers and other body parts get dragged in at the bottom, bit spat out at the top.

Protecting us from getting things being dragged in shouldn't be forgotten 

[mtc]

I run a shark guard on my race bikes.  It bolts to the bottom on swing arm and looks like , well, a shark fin.  The purpose is to keep your foot or other body parts out of the rear sprocket in a crash.  I've seen the results of this type of accident and it's not pretty. In one of my crashes I ended up hugging the rear tire with the sprocket right there...I've seen plenty of bikes that don't run a front sprocket cover.  While this sprocket is inside the frame and therefore more remote, it still poses the same risk should you or a body part like a finger get in there.  I recommend using all the covers/guards.

ouch... i thought it would look better and easier to maintain, didn't think a flimsy 2oz piece of plastic would do anything.