Quote (Blizzard.Net)

if you are banned it will say "your account has been closed (number here)"

Why your account/cd-key has been closed/banned?

(1) Advertising an inappropriate website
Inappropriate websites may include sites that promote or provide game hacks, programs with embedded virus code, pornography, or other destructive or intrusive materials that are not appropriate on Battle.net.

(2) Spamming in a channel
Please be advised thatBlizzardEntertainment has an aggressive stance against any account that is used to spam a Battle.net chat channel. Spamming a Battle.net channel disrupts the normal flow of dialogue in the chat room and violates the Battle.net Terms ofUse Agreement and/or End User License Agreement of the game.

(3) Attempting to obtain passwords
Please be advised that Blizzard Entertainment has an aggressive, zero-tolerance stance against any account being used by someone to obtain or steal passwords or to con or trick users into giving out their passwords on Battle.net. This offense violates the Battle.net Terms of Use Agreement and/or End User License Agreement of the game.

(4) Attempting to obtain CD-Keys
Please be advised that Blizzard Entertainment has an aggressive, zero-tolerance stance against any account being used by someone to obtain or steal CD-Keys or to con or trick users into giving out their CD-Keys on Battle.net. This offense violates the Battle.net Terms of Use Agreement and/or End User License Agreement of the game.

(5) Harassment of other users
Please be advised that Blizzard Entertainment does not support or condone the use of any account to harass or threaten other users on Battle.net. This offense violates the Battle.net Terms of Use Agreement and/or End User License Agreement of the game. Harassment may result in the closure of the account or even the temporary or permanent banning of the associated CD-Key.

(6) Inappropriate use of a bot
Blizzard Entertainment does not tolerate bots spamming chat channels or the use of bots to congest channels, which disrupts the normal flow of dialogue. This directly violates the Battle.net Terms of Use Agreement and/or End User License Agreement of the game.

(7) Offensive or racist comments
While Battle.net is a mature environment, we will close accounts that are used to violate the Battle.net Terms of Use Agreement and/or End User License Agreement of the game. We firmly believe that Battle.net's strength lies in its community, and racist or extremely offensive comments are not tolerated.

(8) This account was detected using a third-party program (hack) with one of our games on Battle.net. This account is now permanently banned
Any third-party program that is designed to affect the way the user interacts with Battle.net is considered a hack program. This includes seemingly harmless third-party utilities that work with the game to provide functions that were not included by the game designers. While many of these utilities might not have been created to disrupt the balance of the game, they alter the original design of the program. The detection of any such program by Battle.net may result in the closure of the user's account or even the temporary or permanent banning of the associated CD-Key.

(9) Impersonating a Blizzard representative
Please be advised that Blizzard Entertainment has an aggressive, zero-tolerance stance against any account used in an attempt to impersonate a Blizzard or Battle.net representative. This offense violates the Battle.net Terms of Use Agreement and/or End User License Agreement of the game.