People often worry about how Google treat buttons that show hidden content on web pages. On example of this kind of button, for those who did not understand, are those buttons in purchasing sites that reveal more information about a service and/ or product. There is no need for you to worry in case your site has this type of button and is revealing useful user related content. As long as your button shows information such as specifications, materials, codes and other information that is about the product you will not have any issues with your site.
You should only worry about this kind of button if the content revealed by it is sort of spammy or even not related to the product or service that you are showing at all. Unfortunately Google has already come across quite a few websites that have a tiny little button that shows a lot of information (such as in long texts) that is not even related to the content of the main page. To top it off, these long texts are filled with keywords which results into spam content. In case this is your situation, then, you should start getting worried.
Do not worry, in case you would like to keep your web page clean and would also like to have users and visitors leave a comment or even reviews, the button technique could also be used, even if people leave huge comments and other texts on it. Google will know how to differ spammy content to real and very user related content, there is absolutely no reason to worry too much about it. Google is used to seeing this kind of content all over the web, and indeed it is quite common to see such buttons on the web. If your site is clean and spam free, relax, you will be just fine.
Video: How does Google treat hidden content which becomes visible when clicking a button?
(YouTube Release: Jul 24, 2013)