Originally Posted by hostxtreem
The way I think of it, .com is the "holy grail" of TLDs. There is no way that Google will treat .co the same due to the fact that .com is so widely used.
For example, if you tell someone a domain, without an extension, they'll automatically think that the extension is a .com.
It's second nature.
Very good point about the second nature. I can see that people are used to .com like they are used to www before the name.