It's actually pretty to have more option than just .com but I'm not sure about trademark conflict. Example if I'm already got twitter.com domain name but if another person got twitter.co domain name what will happen to trademark, if another person want to create a company name twitter but with different dot??. Also if we build up some very good website using .co and the owner of .com with the same name see our idea and want to copy it, which I'm pretty sure .com one gonna win and get all the traffic even they copy us because people might think .com is more exclusive and .co might be only a spam site. Also this might create a misdirect for the site traffic, for example I tell my friends "hay i just found this interesting site last night call digg you guys should check it out!"... I just live it there for ever one to think.....if anyone got a better answer please do tell me.
I do agree with you, first, it will be hard that a serious company leaves out the CO to allow someone else register it, but if they do, bearing in mind that extension might no be that great for them, whoever register a trademark will be at risk of being sued.
What about a general keyword based domain name. e.g. some-ccountry-hosting.com and some-country-hosting.co?
It very much depends in which country do you want to apply for a trademark and whether you want to claim any particular domain name. I don't think that if you get a trademark which features a particular word you could go and claim the same .com domain name.