Mobile payments company Square has just hit 2 million users. They hit 1 million users just 6 months ago. Square is now processing $6 billion in payments on an annual basis. During the same time last year, Square was hoping to hit $1 billion in payments “within the next year,” according to Mashable. Square recently expanded a payment option to New York City taxies and they launched a cash register iPad app this past spring. Square has raised $138 million in funding from investors and is valued at $4 billion.