On two current 11s mechanical road setups, small ring and smallest two cogs will have the chain rubbing the large chainring very badly - so badly that I'm instantly reminded that I need to hit the big ring. I think that on 9s and 10s setups, small-small was noisy as well. My 11s Di2 setup will actually not let you shift to the smallest 2 cogs if you're in the small ring.
Big-big is not as much an issue unless, as stated, the chain is too short. It's a bit noisy, but you can trim the front derailleur. It's also not an optimal gear for the most part, and you will have less drivetrain friction plus noise in the small ring. As already stated, in a road race or competitive ride, you might be in a situation where you need big-big to get up a short steep climb and you don't want to take the effort to drop to the small ring. With the quality of front shifting these days, this may not be as much a factor, especially if you're on some sort of electronic groupset. However, it is an additional button to tap unless you have Shimano's Synchro shifting or SRAM's eTap. (Is there a Campy EPS equivalent?)