You can add Yahoo to the list of companies that have said their business strategy is "mobile first." Google executives have been saying that company's strategy is "mobile first" for some time. Most leading telecom service providers have been "mobile first," in terms of revenue, for some time as well.
Now Yahoo says "we’re moving forward with a 'mobile first' mindset." Mobile first is simply a response to where revenue opportunities and growth now exist.
For Google, mobile first means new applications and initiatives are centered on mobile devices rather than PCs, mobile Internet rather than PC access to the Internet, and the mobile context instead of PC context.
That's why Android, Motorola Mobility and Google Wallet are associated with Google, where it might not have made so much sense in the past.