I just performed two domain migrations to sites that had Black Studio TinyMCE Widget installed and in use. These domains were both on temporary domains/directories ( test.com/beta & whatever.dreamhosters.com/wordpress ) and then after following the standard URL change process - http://codex.wordpress.org/Changing_The_Site_URL - all TinyMCE Widgets disappeared.
Only the TinyMCE the widgets disappeared, while other plugin's widgets remained a-ok.
I can't pinpoint the exact part of the process that caused the deletion, but consider this bug enough of a reason for me to finally create a WordPress.org user account. I've got backups, but it could've been a much more annoying issue.