I will definitely give credit to Google. This was one of the first penalties that they really marketed in an effort to effect change in the web design and search engine optimization industry, and really a change for more optimized websites for mobile browsers, which makes the web more usable overall. Really a pretty great thing for them to have done. Of course there may be more than just an altruistic motive at hand. Consider the cost of crawling nonmobile optimized webpages using a mobile spider, this is quite expensive when you think of all the data across the entire Internet, and consider having to recall it periodically. By forcing optimization and reducing page load time for mobile devices, and reducing the amount of JavaScript and super large files including flash files, crawling has become more economical for the search engines themselves. Though that’s probably just conspiracy theory talk, Google by and large does seem to be pretty goodhearted.