HI Been investing in domain names, and found lots of good names with .de and .co.uk extension commanding a high price. I meant .coms are not a must if the name is good enough? rather have a good .co.uk than a very bad .com right? - for the reg price.
.co.uk can effect search results as search engines might think that its a UK based website. Well there is no substantial evidence on that. Last.fm is doing good.
After course other extensions are worth buying depending on the keyword, the extension, previous resale prices, and some other factors. I just had a blog post on some domain sales this week... check it out. You can see that extensions like .net, .de, and .co.uk are popular and def. worth it. I just spent 3 hours trying to find some keywords in different extensions... . Domain Sales This Week
I believe that it worth to have a look at domain names from the country you are from: .us for USA ot co.uk for UK.