The Per Page Sidebars (PPS) plugin allows blog administrators to create a unique sidebar for each Page. No template editing is required.
Very useful plugin for more complex websites. Works well with WP pages, but would be much more useful if it could utilize custom post types as well.
I haven't disabled it yet, but it definitely shouldn't wipe clean the previously configured widgets. Especially with text widgets utilizing JS or PHP this could lead to losing a lot of work. Please fix if this issue is replicable!