OEM is new. If a chip is returned it has to be branded as refurbished, not OEM. OEM simply stands for Original Equipment Manufacturer--meaning that it was provided without any warranty implied on the part of the manufacturer. I don't know where Heckler got his information but it's simply untrue.
EDIT: And to answer your question, no, there's no harm in buying OEM. Although if you are careful there is almost no way you can destroy your CPU via overclocking, so if a real problem does occur your warranty is likely to hold.