The greatest regret of my professional career is that one year the Association of Moving Image Archivists conference and a furry con happened at the same time in the same hotel. But no one knew in advance, so no one prepared. Can you imagine the cross-programming potential? You could have had some killer panels with speakers from both cons.
Second biggest regret: one year, the Code4lib library technology conference was immediately followed by Faeriecon. Again: there has to be some kind of crossover potential between those groups.

