The Far Lands were an area in the Minecraft world that were the "edge" of the infinite map generater. The far lands start at a X/Z coordinate of 12,550,821 (where prior to beta 1.8 the game generated distorted terrain.) The distorted terrain was removed in beta 1.8, instead the game began generating an endless ocean from X/Z 12,550,821 to ∞. In all versions the game begins generating fake chunks at X/Z 3.0 × 10^7. Lighting also stops working at 3.0 × 10^7. If a player walks onto a fake chunk they'll fall through it into the void. Be for beta 1.8 the far lands lagged very badly. From 1.8 on they no longer lag. From infdev to the Halloween update, the world ends at 3.2 × 10^7. Walking off the edge would cause you to get stuck rather then fall off. | The hard limit where chunks are overwritten is at X/Z of ±34,359,738,368, which is about 23% of the distance from the Earth to the Sun. At X/Z of ±2,147,483,648, (1/16th of the former distance?) , item positions, mob pathfinding and other things using 32-bit integers will overflow and act weird, usually resulting in Minecraft crashing.^1 At X/Z ± 1.798 × 10^308, the position of the player will overflow. Before beta 1.8, the far lands had severe lag, causing slower computers to crash. Another well-known feature of the old far lands was the map taking longer to update according to the player's location. This, however, wasn't part of the far lands, the farther the player gets from spawn the longer the map takes to update, however it's only noticeable when the player gets near the far lands. Weather isn't affected by the far lands directly but is by their terrain. Lightning will hit the top of the map but will be invisible & won't cause fire. Rain particles will be black, snow will fall but not create snow block slices. As of beta 1.6, these affects are only in the far lands.
As I stated above, in beta 1.8 the distorted terrain no longer generated in the far lands, just an endless ocean. The terrain wasn't removed on purpose, it disappeared when the terrain generater was changed in beta 1.8. Like most people, I believe that the far lands distorted terrain should be added back. The terrain looks cooler than ocean & I think Notch should strongly consider adding it back in a near update. The funny looking terrain made the far lands worth melting your computer for. Endless ocean isn't.