It is generally safe to purchase trucks on auction sites, as most auctions have measures in place to protect the bidder during their transactions, such as eBay's buyer protection program. However, buyers should always inspect the listings to ensure the vehicle is in working condition, as some auction vehicles are posted as part-outs, which means there may be major mechanical problems. Buyers bid at their own risk.
The eBay buyer protection agreement allows a buyer to make a case for a refund if there is something wrong with a purchase. In the case of a vehicle, if it is not in the same condition the original listing claimed it to be in, the buyer can open a case using the "item not as described" feature and allow the seller time to make amends.