Some recent remote XUL discussion (here and here) inspired me to create some dialogs for a whitelisting UI for web sites.

When a site wants extra permission:

Clicking the OK button does not allow the application to do privileged operations. Instead, the user must click the Allow button and then click Add in the resulting whitelist dialog, as shown here:

The idea is that the user has to click a series of buttons before the site can do anything, yet isn't particularly tedious. In my opinion, the icons, which are just the site icons, make the dialog look nicer and, in some cases, allows sites to be distinguished better.