Я думал об этом, но появление UAC понятно пользователю. А тихая блокировка запуска - нет. Если сравнивать UX, второе несомненно хуже.
Applications that start when the user logs on and require elevation are now blocked in the logon path. Without blocking applications from prompting for elevation in the user's log on path, both standard users and administrators would have to respond to a User Account Control dialog box on every log on. Windows Vista notifies the user if an application has been blocked by placing an icon in the system tray. The user can then right-click this icon to run applications that were blocked from prompting for elevation as the user logged on. In addition, the user can manage which startup applications are disabled or removed from this list by double-clicking on the tray icon.