In recent Naruto chapters (5 kage summit arch) it was shown that
All members of root (the foundation) have a tattoo on their tongues preventing them from speaking about danzo. This is done so that nobody is able to tell anyone about danzo's secret motives and plans. . As i was re-reading the manga however, i came upon the chapter where sai, yamato, naruto, and sakura invade Orochimaru's lair. Here, sai spills his guts about everything that danzo is planning. How is this possible with the tattoo on his tongue?