I think you are probably seeing this baby in action:
It chucks in your best bid at 5 seconds (or as you specify) before the end of the auction. This can be good or bad.
On the positive side it means you can pop up with a great bid at the last few seconds without ever needing to give Ebay your bid - which as you know Ebay normally uses to automatically bid in realtime. So it is great for those auctions when you don't wanna sit at home like a lemon watching your screen and hitting refresh as an auction ends etc.
However the downside is that you will never win against a higher "maximum" bid that is registered with Ebay directly - because that will always be the "last second" best bid in effect. So "Fred-the-bidder" might be the best bid 5 seconds before the end with €100 Euros, but he has already registered a maximum of €400 direct with ebay - nothing you do with auctionsniper, or a speedy keyboard is gonna stop that. So to be guaranteed the product, and not show your hand too early, your best solution is to add your maximum direct to ebay in the last 10 seconds...but that causes the last minute flurry that you see on the good stuff.
But all said and done Ebay is a great service. No one is forcing you to buy overpriced junk. Occasionally you can get your fingers burnt - I recently bought an electronic item from Taiwan that was DOA (dead on arrival) and they did not refund my returns postage costs!!! So it cost me about €45 to end up with nothing.
But I also sold my Smeg fridge this year that was in my old UK house - I got a friend to take the photos - and got a great price. How impossible would that have been in the old days?