This is my concern, too.
I have a Silver subscription, with an installed, enabled and configured JEvents - Facebook Social Plugin
If I share a category, it contains these tags in the head:
<meta property="og:image" content="{url-of-image}">
<meta property="og:image:width" content="{width-value}">
<meta property="og:image:height" content="{height-value}">
but no og:description tag.
If I share an event, it's head contains neither og:image nor og:description tags.
Shouldn't these tags be enabled Facebook Social Plugin?