Adding a
rel="nofollow"
tag to your link can be very powerful. By telling search engines like Google not to follow the link you can control if your site has certain pages indexed, you can control your link ratios, and you can control your security. Do you really want Google to have a public indexed link to your admin section? This is also something you need to secure with your robot.txt file though.
If you block any links going to a certain folder the no follow tag/code and add a:
User-agent: *
Disallow: /secure/
In your robot.txt file you will be pretty safe.
In fact a recent study at searchlaboratory.com proved almost for sure that the rel=”nofollow” links are honored by Google and not publicly followed. Of course you can only test for what Google allows you to see. Behind the scenes Google can do anything. I think they do follow no follow links and give you a little link juice(PR) good or bad for it. My guess is they follow the no follow links to see what’s there and add that destination as a lower factored backlink.
Who knows, Google is tricky and for the last 5 years seems to cater to big companies that pay for heavy adwords accounts. My guess here is they give a flat PR increase to their high end marketing partners. Sorry for all the speculation!
But if they do cater to these big companies than maybe they don’t care as much about true organic results anymore.
So all in all, Google “does not” register following a rel="nofollow" link. Google might follow the link and use it in the background to factor a websites back-links or outbound-links. After all if you are linking to a virus Google will want to know, even if you have a “now follow” link to try and hide.