Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Big Board operator NYSE Euronext (NYSE: NYX) are living large today, jumping as much as 16.5% on many times the average trading volume.

So what: A fresh buyout proposal from NASDAQ OMX (Nasdaq: NDAQ) and IntercontinentalExchange (NYSE: ICE) has come along to trump the existing offer by German exchange Deutsche Borse. NYSE's board is reviewing the offer and has yet to accept or reject it.

Now what: The NASDAQ/ICE offer of $42.50 per share is actually 19% higher than the old deal, and there's a fair amount of spread between the bid and the current share price. Whoever walks away with the big prize will have created a truly massive, trans-Atlantic stock exchange -- assuming that American and European regulators allow it. That arbitrage opportunity rests on pure uncertainty about the outcome.

Interested in more info on NYSE Euronext? Add it to your watchlist.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.