Blizzard has decided that they will start warning those who use input broadcasting multi-boxing to play both the Classic and Retail versions of World of Warcraft. This announcement comes in a blog post about the policy update.
Initially, the use of software to broadcast your inputs across multiple accounts of World of Warcraft at the same time was not against the usage policies of the game. However, this now changes as Blizzard stated that "As World of Warcraft has evolved, our policies have also evolved to support the health of the game and the needs of the players. We've examined the use of third-party input broadcasting software, which allows a single keystroke or action to be automatically mirrored to multiple game clients, and we've seen an increasingly negative impact to the game as this software is used to support botting and automated gameplay."
They also go on to state that going forward, "the use of input broadcasting software that mirrors keystrokes to multiple WoW game clients will soon be considered an actionable offense."
Starting, players will receive a warning if they are detected to use such software. If the player ignores the warning and continues to use the software, the player may get their accounts suspended, or worse, permanently closed.
This is an understandable policy change. Many other MMORPG's do not allow the use of input broadcasting software is it create's an unfair advantage for others who do not use the software. It can also be easily manipulated for botting or other malicious actions. I agree with Blizzard's view on this type of software.