I have been asked this question by a few affiliates over the years.
.com is obviously king but I think it's worth buying country endings too - for example co.uk I consider valuable.
The .com market is saturated so looking at other endings is becoming a must.
If you type in some of the popular search terms into Google, you will see .co.uk/.de domains (amongst other country codes) in the results nowadays.
I believe it all depends on your target market - .com is vital for an international appealing portal but a UK focused football (soccer) site should use a co.uk for example.
Furthermore, I see a good casino site (ending .ws) that ranks very highly with the big .com portals.
It's all what you do with your site and the end of the day but having country codes may help you too
