Internet Explorer 8 has a new feature that keeps you in control of your search engine default, by informing you when software attempts to change your settings. With this, any toolbar that wants to change the search setting default (by setting a registry key) will trigger a ‘user consent’ dialog, where the requested change is explained clearly, and you are asked to approve/not approve the change. So, no program can silently change your search setting without you knowing about it.
There is also a new API for setting the search default. Any application can call this API, and request that the Internet Explorer Search Default be changed. A dialog box is shown (and the application requesting the change is clearly identified) and the user can allow/not allow the change.