Possible Duplicate:
How does Facebook Sharer select Images?
I'm aware that you can specify a particular thumbnail on any given page by using the og:image meta property. The caveat with this technique is that it doesn't allow a user sharing the URL a reasonable method of changing the thumbnail should other images show on that page. (If this is incorrect, please let me know.)
Is there a way to specify a default thumbnail image but at the same time not alienate the other potential thumbnails that could have been grabbed?