This has to be the most common question on geek message boards, "should I buy a newegg open box?" And these threads are usually spattered with, bitter, anecdotal, uninformed replies by people - for whatever reason - personally didn't have a favorable outcome when they purchased of an "open box" or recycle it from someone who did.
Newegg handles all opened, customer returned hardware pieces by shipping them back to the vender (OEM). It's then up to the OEM as to the extent they test for or repair any defects (and if the OEM knows what's good for their bottom line, they better take their QA seriously.) I believe newegg even informs their customers of this fact in the checkout process when they have an open box item in their shopping cart, at least they used to.
Plus you have to use some common sense here. The number of Newegg returns is huge, and if that's all they did is turn around and ship opened, untested customer returns right back out the door, the number of complaints would very likely be equally huge. Look at most retail review sites, newegg doesn't always appear at the top of their class by accident.