UPDATE: Changes have been made to Google+ and this no longer works. Now, your best option to see categories is to use Google Map Maker. Sorry everyone!
I'm sitting with Joy Hawkins and Greg Gifford at SMX Advanced and they weren't aware that you can click on the categories on a Google+ page to see all the other categories on the listing. If these amazing local search pros weren't aware of this, then I guess a post is in order!
* From our testing, this doesn't always show ALL of the categories - we have seen others in the dashboard - but you will see more than the 2 categories that Google displays on the listing (as long as there actually are more than 2).
Here’s an example Google+ page you can try it on:
I suspect that the reason that this is not well-known is because there is no indication that the categories are clickable. They are not underlined, and when you mouse over them, your cursor won’t change to the little hand icon that indicates a link. You just have to blindly click on those categories to see if more appear. If you don't see more categories when clicking, then it's likely that the business only has the 1 or 2 categories displayed.
This tip can be helpful for analyzing your clients’ categories, and their competitors’ categories.
Stay tuned next week for my theory on “category dilution”!