#0 - Sept. 8, 2010, 8:49 p.m.
Q u o t e:If you feel like this should change, you may want to head over to our suggestion forums and post your thoughts.
One of the big reasons it exists is that gold isn't really a resource available on a realm directly - it's obtained through the efforts of those on the realm, via questing or selling things to vendors. Blizzard even builds in gold-sinks (like the mammoths) to remove some of that generated gold on a realm.
Now, if a player transfers onto a realm and they bring a massive amount of gold, there was no gathering, no questing, no selling to the vendor on that realm. It's just a massive influx of buying power onto the realm with no earlier exchange to the realm. It gets worse when a well-off guild moves. It's harsher to realms that are smaller or newer and don't have multitudes of "wealthy" players already.
So the gold limit exists to prevent this sort of economy destabilizing every time someone new transfers onto a realm.