This article describes how the Australian Olympic Committee (AOC) is banning prescription sleeping pills for Australian Olympic athletes. Per the article, the AOC is concerned about addiction to the sleeping pills after a retired Olympic swimmer, Grant Hackett, said he became addicted to a form of Ambien, called Stillnox.
I'm not sure how banning the use of these prescriptions during the games will prevent athletes from using them after the games are over. Most people who use these medications do not become addicted to them. If the medications improve sleep, this may actually improve athletic performance, as I discussed in a previous blogpost.