This has been a hot topic in the community latety concerning the stealth-removal of the Hot Hot Hot Streak/Flawless Victor achievement without a mention of it in the live 3.1 patch notes. Blizzard now has an official statement about this. The achievement was removed due to an exploit, and it willl be re-implemented at a later time.
|We have removed this achievement and the title it rewarded because it was often being earned through methods that were not what we wanted to encourage. We currently have an idea to bring it back soon, and hope that players with the current titles will get to keep them but we can make no guarantees at this time.|