As if Euronext didn't have enough to worry about on its first day of trading as a publicly traded company. The Franco-Belgo-Dutch exchange saw its shares drop as much as 10% on Friday when it started trading in a disappointing IPO.

To add insult to injury, according to Bloomberg, more shares in Euronext were traded on the floor of its old friend the Frankfurt Stock Exchange, where they are not listed, than on the Brussels stock exchange - where they are...