Pocket

To completely uninstall the Pocket extension, follow these steps:

1. Open Pocket

2. Click Options (looks like a cog wheel)

3. Select "Account" on the left

4. Click "Logout"

5. Click "Erase my local data"

6. Uninstall the add-on (go to Tools | Add-ons, select "Extensions", and click the "Remove" button for Read It Later)

7. Open your Firefox profile directory and delete the "Read It Later" folder and the "readItLater.sqlite" file

That should do it!  

Note: If you were a previous version 0.9 user, your old bookmarks may be in Firefox's bookmarks.  Open FF's bookmarks and look for a folder named 'Read It Later'.  If it's there, delete it.