Funny this should come up as just yesterday I was planning to revisit the addthis.com method of doing this. Have been using it for some time on a couple of sites that are such that I didn't care if the image matched the product shared.
From their https://addthis.com/academy site, they talk specifically about specifying the page tags to truly make add this work.
<meta property="og:title" content="AddThis Tour" /><meta property="og:description" content="Watch the AddThis Tour video." />
<meta property="og:image" content="http://i2.ytimg.com/vi/1F7DKyFt5pY/default.jpg" />
<meta property="og:video" content="http://www.youtube.com/v/1F7DKyFt5pY&fs=1" />
<meta property="og:video:width" content="560" />
<meta property="og:video:height" content="340" />
<meta property="og:video:type" content="application/x-shockwave-flash" />
Specifically, for 99.9% of the cases where I want to use this, I was going to look at getting help in turning the red image code```
<meta property="og:image" content="http://i2.ytimg.com/vi/1F7DKyFt5pY/default.jpg" />
Propagating it with ZC code versus having to take the time to enter the data manually
Results from their [debug tool](https://developers.facebook.com/tools/debug) shows that a standard 1.5.7b install just needs an accurate og:image to work. Of course, they want you to add all the og tags but it would work with just the og:image listed correctly. I have no idea how it currently picks an image but, it is NOT the one for the product ID.
Maybe others will jump in here with possible solutions to generating the meta tag.
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