Ebay has a problem that seems very difficult to resolve, so it seems that the best method of handling this is to pass this information along to your trading partners.

Malicious ebayers will send emails to your bidders to tell them that your item is a fake or that it is a piece of junk or that you cheat people in order to cause your bidders to retract their bids.

The goal of these malicious ebayers is not to warn you about a possible scam, but to drive the price down so they can purchase the item at the lowest possible price.

The way we look at is this:  Ebay's system (including Paypal) is good at protecting buyers.  If somebody takes the time to list an item, then the odds that are that it is a legitimate item. 

In our eyes, the actions above are very similar to "bid shielding" which is against ebay rules.

Just do your due diligence on the product you are looking at buying and take with a grain of salt any emails that you receive that are negative about the seller or product.

Sellers can always make their feedback and auctions private to prevent this type of malicious activity.

Good luck in your bidding and selling.