Just read this article about eBay motors on Jalopnik..
From this page [pages.ebay.com]
Policy overview
A non-binding bid is a bid that shows a buyer's interest in purchasing an item, but it doesn't create a formal contract between the buyer and the seller.
All bids made in the Real Estate and eBay Motors vehicles categories are considered non-binding.
Remember, bids placed in any other category are a legal commitment to purchase the item. We strongly encourage you to read the other terms for more information.
Make sure your listing follows these guidelines. If it doesn't, you may be subject to a range of actions, including listing removal, limits on your buying and selling privileges, and suspension of your account.
What are the guidelines?
Allowed
Using listings to find buyers who are interested in purchasing your item Including information about what buyers will need to do next (for example, deposits, transfer paperwork, and transportation options) in your listing. Adding a reserve price to your listing so that your minimum price is met.
Not allowed
Bidding without the intent of completing the purchase
Retracting a bid on an item that doesn't fall into a non-binding bid category
Backing out of the transaction due to buyer or seller remorse
------Backing out of the transaction because buyers didn't place a high enough bid and the seller didn't add a reserve price------
Stating in the listing that bidding could result in a binding obligation to complete the purchase