I tried to reach the far lands by teleporting relative to my position. When I was at 23.000.000 ~ ~, I teleported another 10.000.000 in x-direction. But all I got was a message saying "Connection Lost, Illegal position". So far so good, I passed the world boarder, but there was a button that said "Back to server list" and it takes me to the server list, even though it was a single player world I played in. And it really takes to the multiplayer server list. Also, I am not able to join the world again, since I am still past the world boarder. Not that this is a hughe loss, since I created the map for this purpose, but it could lead to tears, when someone does this in a serious world.

So, steps to recreate:
1. tp to around 33.000.000 blocks
2. get "Connection Lost" screen
3. Click on "Back to server list"
4. Open world back up
5. Still get the "Connection Lost" screen