RAM is a volatile memory. This statement is almost true but there is an exceptional case where it may not be. RAM sticks do not lose their memory instantly when you power down the computer. Residual memory takes some time to degrade. When the RAM is cooled down, it even takes a longer time; enough for an attacker to plug it to a live OS and dump the contents from the stick to a harddisk. This is a well known exploit called as the cold boot attack.