At the end of "the world" you can keep going with the camera to go super far. If your mouse is laying in a way the cursor is moving up, down, left or right you are screwed! :)
For games like that, infinite world is a problem because the bigger "visible" world, the bigger performance issue and developers can't predict how far players go. Other problem is traveling and transportation on big distances.
I think that better choice would be looped world like planets. In that way you don't have borders and still maintain fixed size of the playable area. Adding layers (underground, next planets) can expand playable area to enormous size and add different environments without worrying about smooth transitions between them.
