1. How to create undetectable cloaked nofollows in Wordpress .
2. Why it is almost always a bad idea to do this.

How to cloak nofollows so only the Googlebot sees them.

1. Prevent anyone other than Google from loading your site using the Google user agent. The purpose of this step will be to prevent detection. This can be done using BadBehavior or Noobliminal's script to verify spiders.
2. Insert a few lines PHP code at the top of your Header.php code. This code a) detects the Google user agent, b) checks if this is the page you want to cloak and c) if both occur, it adds the new Robots Exclusion tag. Here's the code to cloack-nofollow my 'page 3' in a Wordpress blog. $user_agent = $_SERVER["HTTP_USER_AGENT"]; if(preg_match("/(google|mediapartners)/i",$userAgent) && is_single('3')){ header("X-Robots-Tag: nofollow"); }

Cloaked nofollows using "X-Robots-Tag: nofollow" is a bad idea.

1. It's unethical: There are legitimate reasons to nofollow links. However, only reasons I can think of to cloak a nofollow tag are either to deceive advertisers who pay you are to gip people you promised link exchanges. If want to "nofollow" every link on page 3 without cloaking, delete this bit in the if statement: "preg_match("/(google|mediapartners)/i",$userAgent) &&". That will nofollow the link for everyone. But if you are a bit evil, you're still tempted, right?
2. You will probably make your blog drop out of the SERPS! Why? Well, when you nofollow this way, you no follow every link on a page. This means you will nofollow links you want followed. If you nofollow only one page, this probably isn't an issue. But suppose you begin trying to get clever and nofollow your whole sponsored category? Or every page that contains at least one paid link? Yes, you'll avoid any Google penalty for paid links. But Google will stop following your internal links. Then, unless you are very, very careful, and very very clever, you will soon find your blog dropping out of SERPS for everything. So, massive nofollowing using the "X-Robots-Tag: nofollow" will probably hurt you more than anyone else!
3. Cloaking violates Google's guidelines. Now, this might seem like an odd reason. After all, the reason one might wish to nofollow is to obey the guideline of "nofollowing" all paid links. But you don't need to cloak to obey that, right? You can do nofollow publically-- letting everyone including advertisers know what's up. But, if you try to conceal this from the advertisers by cloaking, you violate a second Google guideline. Only Google can catch you, and we don't know what they would do. But, given the negative impact that will come from nofollowing all your internal links, why risk getting an additional penalty for cloaking?

That's how you cloak nofollows... and why you shouldn't!