Starbucks announced a deal that will see it begin accepting payments from Square’s Pay with Mobile transaction as well as processing Starbucks’ U.S. credit card and debit card transactions. Starbucks will also invest $25 million in Square in a move that values the company at $3.25 billion. This is a big deal on several levels: Starbucks runs a mammoth retail business, of course, and much of its middle and upper class user base is already paying for their coffee with their phones. Perhaps the biggest win for Square here, though, is in introducing its offering to a bug base of mainstream users. When I talk to my friends and family about Square, I usually get blank stares. This tie-up might be a big step toward addressing that.