<< I woke up to two ebay notifications today, one saying I had received an offer on an item, and another saying 
that offer had been withdrawn. Apparently the reason is "entered wrong amount." >>
 
Cancelling an offer (a buyer doing this)  is treated the same as retracting a bid.  The reason bidders choose 
"entered wrong amount" is because there are not enough honest choices, such as "changed my mind".  
In theory, I suppose, one could say then that in such circumstances any amount would be a wrong amount, so 
in a way it is not always a total lie.  
 
Look on the bright side, -- better a retraction than having to contend with an Unpaid Item.  Here is the ebay page 
about it if you want to see:
http://pages.ebay.ca/help/buy/bidding-overview.html#change