I just bought a domain with .com for my website but I found also .co also....It's a domain with dot.co will have a problem with google search engine? also will dot.co become a future of .com ??
.co is a special gTLD/ccTLD like .tv & .me .co works like .com on google search engine, the only difference is that it's one character less. .co & .com are globally recognized as "commercial" and should not be compared with .net .org .biz .info ...ect .co was the extension of colombia but now it's in the hands of a company in florida.
earlier .co was the extension of colombia, now its global and mostly used for representing company (.COmpany)
also, .co is a little more expensive than .com, but you may get more chance to get better domain name