Some folks that I respect were giving me a bit of a hard time because they felt like I punted on this webmaster video:
So let me take another stab at the question, and tell me what you think. There’s a couple effects going on:
– first, we’ve been making changes that make it much more likely to see .coms in the UK. I’d say that’s 80-90% of the changes that people are seeing. Most of the generic TLDs (.com, .net, etc.) that are showing up now are .com sites like tescofinance.com and churchill.com that are relevant to the UK even though they don’t end in a .co.uk.
– I’ve been following some of the examples people have pointed out. I remember kiva.org in particular was mentioned and that probably is off-topic for the UK. I dug into that one, and it was an unrelated ranking experiment that was going on that we changed.
I’ve been trying to keep up with the examples that people have pointed out, and most of the examples that I’ve seen have fallen into one of those two categories. If people want to point out examples of off-topic .coms that I’ve missed, I’m happy to poke/prod the appropriate folks at Google though. Feel free to leave comments like “For the query [red widgets] on google.co.uk, redwidgets.com shouldn’t show up because they don’t really provide red widgets to the UK.” Then I’ll ask the appropriate team to check out the comments.
Update, May 31, 2010: In the last few weeks, engineers have launched more changes that should do better at returning (for example) UK websites for searches done in the UK. If you still see mismatches (e.g. searches in the UK returning sites from Australia or wherever), feel free to leave a comment with the search query and the mismatched domains that you see.