Microsoft's Larry Hryb, aka Major Nelson, has told gamers on his blog not to share their accounts with friends or tamper with game saves.
The Xbox Live director of programming stated that those who refused to heed his warnings could find that they permanently lose their account. Hryb says that some gamers are giving in to the temptation to give their account ID and password to people in return for promises to build up their score on games such as Halo 3.
While on the subject, Hryb also commented on the dangers of using "nefarious techniques" to increase gamerscores and obtain achievements. He said, "Let me be more clear: If you use tampered gamesaves to boost your Achievements and Gamerscore, you may sign in to Xbox LIVE one day and discover that we have removed your Gamerscore. Once we do that, you will never be able to re-earn those achievements on that account. Even worse, you might have your account and/or console banned from Xbox Live."