This happened to me several years ago when the volcano in Iceland was causing problems. 3-1/2hrs into a flight from ATL to Europe they turned us back. Mileage credit didn't post, but I complained vigorously yet politely that I had spent 7hrs in the air and should have something to show for it. I finally ended up with a mileage credit applied to my Skymiles account which ended up being almost twice what I would have earned for the trip itself. The caveat was that this mileage credit didn't count towards mediallion status, but considering the amount of flying I was doing at the time it didn't really matter.
For 15/30minutes, though, I think there is less of an argument for the inconvenience of it all.