Google's latest Webmaster Help video deals with ccTLDs and geotargeting - specifically Google's view of a developer grabbing a ccTLD that is generally associated with a country they're not actually in. Here's the exact question:
As memorable .COM domains become more expensive, more developers are choosing alternate new domains like .IO and .IM - which Google geotargets to small areas. Do you discourage this activity?
"I want you to go in with your eyes open," Google's Matt Cutts responds. "Because you can pick any domain you want, but if you pick a domain like .ES or .IT because you think you can make a novelty domain like GOOGLE.IT ('Google It'), you know, or something like that, be aware that most domains at a country level do pertain to that specific country, and so we think that that content is going to be intended mainly for that country."
He does note that there are some ccTLDs that are more generic like .IO, which stands for Indian Ocean, but there are "very few" domains that are actually relevant to that. A lot of startups were using it, and it was something that was more applicable to the entire world, he says. For reasons like this, Google periodically reviews the list of ccTLDs, looking for things that are in wider use around the world. This way, it can view sites with these domains as more generic.
Here's a list of the domains Google considers generic.
Cutts talked about this topic in another video earlier this year, specifically responding to the question:
We have a vanity domain (http://ran.ge) that unfortunately isn’t one of the generic TLDs, which means we can’t set our geographic target in Webmaster Tools. Is there any way to still target our proper location?
You can see his response to that one here.
On a semi-related note, last week, WordPress.com started letting users register .CO domains.