Just say no
Toolbars just hog browser window space and other PC resources, space and CPU, etc. The browsers take long enough to load as it is, with checking all the add ons, etc for updates.
Toolbars can cause conflicts with other software - I ended up having to remove Google toolbar from my Dad's PC due to a conflict with another piece of software, after eventually tracking it down to that.
Toolbars get installed far too easily by those not in the know as every other program decides to suggest you need Google/Yahoo/etc toolbar. So much so, that users can have multiple toolbars installed and think they are removed by just disabling them. I've seen computers with loads of these.
The average user could also pick up malware from installing what they think is a genuine toolbar.
And really, what is the point? There is already a search box in the corner of IE/FF/Safari/etc, there is no need for what, to me, is really a more glorified search box.
As for this new feature, won't the comments be mostly falling on deaf ears as the world and his dog does not have Google toolbar, nor feels the need to install it. Don't get me wrong, I like a lot of Google services but cannot stand browser toolbars. The gain does not outweigh the problems they cause, as far as I can tell.
Rule of thumb for me, just don't install any toolbars, so I won't see this feature, apart from when fixing other user's pcs, no doubt.
Shouldn't they be able to provide the information stored about your site, without forcing you to install the toolbar, under the data protection act, at least in the UK?