"But protecting the naïve user from the malicious attacker can mean the blameless developer loses a feature they were relying on. Vista Beta 2 secures what's just been renamed Internet Explorer 7+ by running it in a new protected mode, which restricts the changes IE can make to the registry and the files it can update; but other security-related changes apply to IE 7 for Windows XP as well.
Take the phishing filter built into IE 7 to spot fake sites; this has already been triggered over 170,000 times during the beta, which is good news - if they're really fake banking sites or some such. But what do you do to make sure your site doesn't trip it accidentally? " - The Register