I've been using the Google toolbar for a long time, but no more. Now I'm using the MSN toolbar instead. Why? Six simple reasons, five of which are security-related:

1. The MSN toolbar doesn't index the browser cache or history file. That means that it won't find cached information like credit card or online banking statements.
2. Every user on a multi-user machine has a separate set of index processes and files.
3. The MSN toolbar never sends any data back to Microsoft. Google's toolbar, of course, sends tons of data back to Google, although they're up-front about it.
4. Index files are obfuscated, raising the bar for casual snoopers (of course, snooping requires admin privileges in the first place :)
5. MSN never automatically downloads updates. You can ask it to do so, but you don't have to.
6. It searches Outlook.