Google finally published Authorship FAQ yesterday and @marktraphagen created useful takeaways and shared them in Google Authorship & Author Rank community (which I happily help moderating).

The most important takeaway:

Authorship annotation is useful to searchers because it signals that a page conveys a real person’s perspective or analysis on a topic. Since property listings and product pages are less perspective/analysis oriented, we discourage using authorship in these cases. However, an article about products that provides helpful commentary, such as, “Camera X vs. Camera Y: Faceoff in the Arizona Desert” could have authorship.

Going further into the topic, Google discourages from featuring authorship on the home pages and category pages as well:

• The URL/page contains a single article (or subsequent versions of the article) or single piece of content, by the same author...

• The URL/page consists primarily of content written by the author....

[Now gone to figure out hot to remove my authorship from the home page of the Wordpress blog which is too old to be too flexible]