Affects Version/s: Minecraft 1.4.2
Fix Version/s: None
Currently, only 3 strongholds generate in a triangle-shaped distribution around the world's original spawnpoint. Jeb mentioned on Twitter quite a while ago that Strongholds would eventually generate in an unlimited fashion, equally distributed throughout the world, but the 3-stronghold limit is still in effect.
Given the fact that Vanilla now has the ability to change spawnpoints and that Minecraft's maximum possible land area is greater than that of the Earth itself, it makes little sense to limit strongholds to such a small area, especially since more and more content depends on traveling to The End. This is doubly difficult for large servers that relocate the main spawnpoint and have dozens or hundreds of people coming through that want to travel to The End. Having a larger supply of Strongholds would help relieve the strain on the only 3 entries to The End in the entire game.
I'll add a comment linking to Jeb's tweet as soon as I'm able to track it down.
Thanks for reading!