Caydiem, the most intelligent and experienced community manager in World of Warcraft (not a case it’s a ‘she’), wrote on the official forums a silly explaination about the policy on Player Gatherings:
Regarding Player Gatherings Online
We fully understand that players may be dissatisfied with certain aspects of the game, and we appreciate when these players constructively make their voices heard in our forums. We use the forums to interact with the community, and the forums provide a large sampling of what players like and dislike. While we might not be able to respond to every thread that highlights an area of concern, the forums are read actively, and the game designers remain fully aware of what those areas of concern are. As such, the forums are the appropriate and intended place for these types of discussions to take place.
We do encourage players to hold events and strengthen the bonds in their community. But as for gathering in game for the purpose of expressing dissatisfaction with an aspect of World of Warcraft, please be advised that we cannot allow such protest gatherings that cause severe lag and/or server crashes to occur. If a gathering occurs that causes these issues, players will be asked to leave. If they continue, however, GMs can and will take action against accounts. This can lead to a suspension. Keep in mind that holding gatherings that cause undue server stress affects everyone on that realm. Please be kind to your fellow players and respect their desire to play too.
So, as you can read, there is ‘bad’ and ‘good’ lag.