The OS X trash is a relatively simple concept: you put something in it as a temporary location before you throw it out, and when you do throw it out it is for the most part permanently removed. The trash has been this way for years, with the only additional option being the recent "put away" feature in Snow Leopard. Despite its simplicity, periodically you may run into problems with how the trash behaves, such as the inability to remove files from it, or the system warning about files on local drives being removed immediately.
