OCZ & Toshiba send out new units.
Sammy sends out "refurbs".
I really doubt that they can refurb a SSD in any meaningful way, besides maybe recycling the case and or PCB.
There is no way that they can affordably test the NAND to see how much life is left for each return, so, it is my understanding that the units they get back, they take out the NAND, and sell it to the USB pen drive makers.