> Google is an advertising company, not an Internet search company.
I would avoid defining a company by its current monetization strategy especially in an industry where monetization is frequently an afterthought (it was for Google).
Furthermore, it doesn't do much to define a company since there are only so many monetization strategies.
What if we'd start defining companies by whether they are "for-profit" or "non-profit" instead? We'd end up with such non sense as "Google is a for-profit company, not an Internet search company." Or with, "B2B" vs "B2C": "Google is a B2B company, not an Internet search company."
If you are going to pick only one thing that defines a company, at least pick something that really makes them stand out (Google - search, Apple - consumer electronics, Facebook - social networking, etc.).