Google is the biggest KM company

Google Co-op
Except co-op, google also provide google groups
For both products, google claim that they want to help each others to share knowledge and experience.

And for Google itself, it's the most poluar tools for people to find useful information(or knowledge ) for themselves.

And based on above facts, in some degree, we can make a conclusion that now Google is already the biggest KM company. The only difference is that google provide tools for individuals, but others provide tools for cooperation. But, none can't say that google tools can't be used in company, which means, if google want, he can act a role in KM market.