Face: Just keep it up, Nose, you are not indispensable.
Nose: Go for it. I dare you...

As per a deeper thread in WMW, the above would cause an infinite loop.. try the code that JDMorgan, resident apache guru recommended..
[quote]
If installed in .htaccess, that code will cause an 'infinite' loop, repeatedly rewriting nogtb.php to itself until the server gives up. Fix for use in .htaccess:

RewriteEngine on
#
RewriteCond %{HTTP_USER_AGENT} GoogleToolbar [NC]
RewriteCond %{REQUEST_URI} !^/nogtb\.php$
RewriteRule ^ /nogtb.php [L]

or in more-compact form

RewriteEngine on
#
RewriteCond %{HTTP_USER_AGENT} GoogleToolbar [NC]
RewriteRule !^nogtb\.php$ /nogtb.php [L] [/quote]

How to do it for Wordpress based blogs?

I tested the code before posting it. There is no feedback loop. It redirects and stops. At least on my server. The UA in the code you posted is not what shows up in my logs. To be safe you can block both 'GTB' and 'GoogleToolbar'.
So taking the best of both:
RewriteCond %{HTTP_USER_AGENT} GTB [NC,OR]
RewriteCond %{HTTP_USER_AGENT} GoogleToolbar [NC]
RewriteRule !^nogtb\.php$ /nogtb.php [L]

@Jack: adding this to your htaccess will protect your Wordpress site.

The problem with this code is it will block google toolbar users from using your site. People need to aware of this before using the code as it could have a deep impact on their site traffic..

The worst thing about that piece of code is that it doesn't makes nay difference from toolbars users with latest version or those who have not updated and therefore know nothing about Sidewiki.

You won't be only blocking GTB users, but also many will be dissapointed because they do not even know what's all about.

It would be nice to have an option to opt-out from Sidewiki (which is not a wiki because no one can edit it), as we have with the MS image toolbar, but blocking GTB users is way too much, IMHO.

OK, just did a quick check: it will still block GTB users, but you can restric it to the latest version just by changing the string check GTB6.

eltercerhombre - That is why I am working on a actual solution right now to block sidewiki itself and not the google toolbar owners.

This is something that google should have never released and should have known better. I think they will find that this is one thing on the internet they will not control, our sites!

James

Completely agree with you James: Google should have never released this. But they did.

Now we have only 2 options (let them do is not one): make enough noise so they agree for a opt-out option or find the way to block.

I agree that blocking all Toolbar users is too much, but until we can narrow detection to just SideWiki then the only other option is to pay for SSL for each site; SideWiki currently doesn't work on SSL sites.
@James - I've tried UA strings, a modified version of AutoBlink and even screen width vs. browser width to detect SideWiki without success. Mind sharing your approach?

While I can not say what I will be doing, I will say it will not involve any javascript. I have a working version but still need some tweaks and mine will also have an admin area giving the site owner a little more control.

I have 12 SSL certs but I have way more than 12 sites and I know many that have more then me so even the SSL route could get expensive and even then google "hints" that they are going to fix that "bug" ...

James