It had to happen eventually. Jasper's Corner Tap & Kitchen in San Francisco has put a Negroni on tap.
The kegs were pretty large, so as Kevin Deidrich explains in the video below, they used two bottles cases each of Plymouth Gin, Campari, and sweet vermouth to fill the keg. Then it's pushed through the line by an inert gas (that doesn't carbonate it but does prevent oxidization) and out of the tap.
They serve it on the rocks with a slice of orange. I had one last night and it tasted just like a Negroni, but, you know, more fun.
The Negroni will be on draft at Jasper's for a couple months. Get 'em while they're hot!