Today, I wanted to buy a player that I had carefully chosen. I did a first bid and, some time later, somebody did an higher bid. Then the server got down and, for about half an hour, I couldn't connect and make an higher bid. And the auction finished ONE minute before the server got online again.
Therefore, the other guy won the auction very easily, and the vendor didn't sell the player at a price he could expect (and me, I lost a player that I really wanted to buy...).
When you are doing maintenance like that, you should extend all the auctions of the same time that the server had been down.