Is it weird that Google's mission statement doesn't describe their primary revenue stream? I suppose they could say that they're making information universally accessible and useful to individuals as well as advertisers. But I don't know, their mission statement makes them sound like the best library ever. Not an advertising company.
It's becoming an bigger and bigger stretch to wrap that mission statement around what Google does. Reader was a great tool for organizing information--they killed it. Cell phone hardware has very little to do with organizing information, but they spent $12 billion on Motorola.
I dont see an issue with investing in mobile. The cell phone is (mostly) a new distribution channel; a means of reaching consumers. It was critical that Google have unfettered access to its users, although these days mobile is increasingly a producer of information to be collected and organized.
Apparently, they see advertising as a means to an end. At least, that is what one can deduce from comparing their mission statement with their activities.
Google Search, Google Scholar, Google Books and Google Maps are what they want to do to collect the information, and they think they need mobile phones and self-driving cars to make it universally accessible (that, or that is on the fringe. A mission statement has to ride between being too vague and only barely describing parts of the business)