This plugin has not been updated in 438 days; but why should it be when it continues to work great.
I just looked at several currently listed open graph plugins before installing this one in a new website, and none of them could pick up my default image or were much too complicated to setup (you don't need a Facebook App to pull an image to display in Facebook).
I installed Open Graph Pro, filled in one line to replace the header image, ran the Facebook Object Debugger and voilà, there was my default image.
I did get a parsing warning, but I don't care; Facebook picked up the website name and discription, article names (with website name) and excerpts, the image for my website, and all of the articles featured images... IT JUST WORKS!
The parser's result for this metadata did not match the input metadata. Likely, this was caused by the data being ordered in an unexpected way, multiple values being given for a property only expecting a single value, or property values for a given property being mismatched. Here are the input properties that were not seen in the parsed result: 'og:type, og:title, og:description, og:site_name')