Open fermentation is more common than one would realize. There are commercial fermentation vessels made for open fermentation. The fermentation is started in the open vessel and with 3-4 days of pitching is transfer to a conical to finish. It's used to brew Belgian style and it's said it increases yeast character. I've seen it used at Harriet Brewing in Minneapolis. The brewery is now closed, but the vessels were from Germany and I'm assuming being used somewhere else.
English beers are also brewed in open vessels, Samual Smith out of Tadcaster is one them. They're brown ale is an example of open fermentation and it's a fantastic beer. Lots of fruity esters.