15 Land?

Over on StarCityGames.com I was just reading about a 4 colour deck (two splash colours) that ran only 15 land and was contemplating only 14 (link). On Sunday at the Games Village Sneak Peak I ran a 3 colour deck (all three colours in equal numbers) and only ran 15 land in it and never had a single problem with only 3 extra mana producers. So just how low will land counts go?