In the UK at least it feels very much AOL --> Facebook, and for what it's worth I've always assumed that in that aspect we are just mimicking America (without having bothered to confirm that assumption).
From (roughly, from memory) 2000 to only a couple of years ago I was regularly seeing "AOL Keyword: <blah>" in video more traditional (print/real-life) advertising. The biggest example that comes to mind is movie trailors, they ALWAYS promoted with AOL, but plenty of other brands were, too.
Possibly the reason I always assumed that it carried over from America was the fact that, at least in my corner of England, AOL were reasonably irrelevant. I mean, they weren't unknown, or even unused, but they didn't exactly seem like a big player. (Again, this was during the latter part of my childhood, so this is from memory of my experience, not from analysing businesses at the time.)
I'm in the UK and see the same thing all the time. Just this morning I saw an ad for chips with a Facebook page URL at the bottom.
http://www.facebook.com/McCainRusticChips
Chips! On Facebook!
That said, you've got to admit that this is a different phenomena than AOL keywords.
I've seen plenty of brick-and-mortar businesses lately that have a sign up proudly declaring "become our fan at facebook.com/abc", and I'm not even located in the US! I've encountered these signs in Australia and New Zealand, for what it's worth.
In contrast, I don't recall ever seeing a sign up saying "Remember, our AOL keyword is 'abc'" or anything along those lines. The phenomenon is reminiscent but not comparable at all, in my opinion, if only because AOL was lacking the social aspect completely.