Infinite Sandboxes

Sandbox, a concept that video gamers either love or hate; the idea of being able to roam freely around an open world. To most people the freedom of an open world sounds like a great idea - but there's a problem.

That problem is when those endless worlds become just that, endless - and that can be boring. You end up with a sandbox like Cyrodiil in Oblivion - trees, trees, hedge, trees, hill, trees, random bandit, trees, trees etc. Trust me, it gets very boring, especially when you have no clear objective.

So what are the advantages and disadvantages of sandboxes in gaming?

Advantages
1) Free reign/choice - the player can do what he wants - he/she has actual control over his/her character
2) More immersive - because the player is able to explore more, he/she can get more involved in the world and it can seem more real, they can become effectively more immersed

Disadvantages
1) Repetitiveness - The sandbox can become extremely boring when the developer doesn't put enough work in to fill the world with different, interesting things to keep the player hooked.
2) Workload - For a developer, making a sandbox game can be a heck of a lot of work leading to a game being released half done.

Take that as you will, I probably missed half the stuff there. Post in the comments if you have any suggestions.