Turns out the spoon has nothing to do with it. Robert L. Wolke, the food scientist and author of What Einstein Told His Cook 2 has debunked the spoon myth, saying there's nothing about the handle of a spoon that will keep champagne fizzy.
The truth is that champagne simply does not go flat as fast as beer or soda because it is clear. He writes:
In order for a dissolved gas to escape from a liquid, the gas molecules must have a microscopic speck of material (a nucleation site) upon which to congregate until there are enough of them to form a bubble. The main reason that true Champagne stays bubble longer is that it is extremely clear and speck-free.
Then there is an explanation of the process by which true Champagne is clarified. So we're guessing that cheap sparkling wine may not stay bubbly as long. Another tip: Make sure you refrigerate it. Carbon dioxide stays dissolved to a greater extend in cold liquid.
For us, the shiny spoon peeking from the back of the fridge is at least a reflective reminder to make mimosas in the morning....
Buy Wolke's book: What Einstein Told His Cook 2, at Amazon