I really appreciate your helping Ipstenu, thanks so much. :)
I don't think it's actually the hosts anymore. Both are now getting the correct
<link rel="image_src" href="http://www.mysite.com/image.jpg" /> in the
<head>, but now neither is supplying that image to Facebook.
I thought the blog on HostGator was working before because I only had 1 picture in the post and no comments (w/ avatars), whereas my blog on BlueHost has multiple pictures in the post and lots of comments (w/ avatars), so when I posted the link to Facebook, it only gave me one picture option (which is what it did when it was working, gives you only 1 option, the picture I specify).
(For all of this testing I've been posting the link to Facebook by hand rather than through Twitter btw.)
So what I did was disable all plugins on both blogs and switch the themes to default (kubrik). I added the function into the default themes functions to get the Facebook image, and checked the page source to make sure it came up on both blogs, which it did.
I still had no luck when I posted those links to Facebook. Facebook is not recognizing the
<link rel="image_src" href="http://www.mysite.com/image.jpg" /> for whatever reason.
I'm looking back through my Facebook updates and it looks like the last time things worked for sure was December 18th. December 21st and onward is when things haven't been working. I think that may have been when I upgraded to 2.9, I just didn't realize the problem was occurring at the time (holidays going on etc...).
SOOOO I think it's something on the WordPress end. I find it unlikely both BlueHost and HostGator acquired issues at the same time, and like you said if it was a FB issue then like you said, a lot more people would be complaining.
I guess I'll send something to the WP guys, hope they can look into it. :) Just not sure where the best place to file this...