Comment on Google Authorship Tutorial by SEO Dave.
You have to set it up as described above or use another method. Google has changed what works a couple of times and I’ve had problems getting some sites to be considered mine (get my Google Plus image associated with SERPs) so I’m not 100% sure how it works!
I was about to say I setup everything correctly for this domain, but 6+ months on my SERPs still don’t have my Google+ image associated with them, just checked and it is, yeah :-)
I wrote this article in July 2011, I setup highlighting code for this site before the end of July and it took over 6 months to work! Another site I setup at the same time took about 3 months for the images to show up, so be very, very patient.
Check the Google Webmaster Tools Rich Snippets Testing Tool for your domain and if it says you have it setup correctly WAIT months for your Google Plus image to show up. If it says something isn’t setup correctly fix the problems.