Just a few hours ago, a post popped up in the German WoW-Forums where a player asks for help as he has reached WoW's gold limit.
The posting player says, that he has always seen World of Warcraft as a trade simulation, so his motivation to play the game was not going further and further in the content or doing PvP: No! Three years of trading, and trading only earned him 214748 gold, 36 silver and 46 copper.
He has reached the limit of gold a player may own and asks for help about that. The player doesn't get any single copper from selling stuff any more.
A gamemaster also confirmed the gold limit and also admits that he and his team are quite amazed that someone was actually able to reach it.
http://nihilum.mousesports.com/en/news/273,player_reaches_gold_limit_in_world_of_warcraft/