People make mistakes. A core principal when designing software is to plan and expect mistakes. The user interface should anticipate human errors and allow people to make mistakes without punishing the user. Recently after watching a show on Tivo the interface offers to delete the show or keep it. Moving quickly I deleted a show that I had only partially watched. The show was still stored on the Tivo, when I pressed delete it only marked it for deletion, but there was no way to get it back.
The recycle bin is a great example of a UI safety net. If you delete something you can still get it back. This has two advantages: If you delete something you can still get it back. The second advantage is you no longer have to offer a secondary confirmation screen for every deletion. Win-Win.