The Heritage/REA examples are more akin to changing/lowering/raising your SNIPE bids with ebay.... which I am sure we have all done at some point.
I personally tinker with my snipe bid amounts all the time, based on another pricey item I may have won recently, or a car needing unexpected repair, or a better-than-expected bonus at work, etc.
The bid amount really doesn't matter until the snipe goes off. Bid retractions, on the other hand..... not ok!
There's a huge difference between the two.