I’m not seeing much uptake on this… it seems like a bug to me. Unless there is a checkbox control to turn Onebox refresh on and off?
As an example of an alternative approach, this page lets you test your meta data to see what you will get, but it is also a front end for the Facebook cache.
Funny that their OpenGraph tag appears to be broken! 
If you try an URL in this tool it will fetch the cache results, and then gives you a button which you can use to re-scrape the site to update their cache.
That might be a nice option for this tool… perhaps a button that comes up when you hover over an URL which is in the cache?
As it is my first tests while implementing this feature will always be what shows on certain links.