VeriFone (PAY) is giving up on mobile card readers, citing the high cost of acquiring customers for a low-margin business. "Our experience ... tells us that the standalone economics of micro-merchant acquiring are fundamentally unprofitable," said CEO Doug Bergerson during VeriFone's FQ4 earnings call - it was only in May his company launched its Sail card reader. Did Square's unmatched scale drive VeriFone out? And if so, does it bode poorly PayPal and Groupon's efforts to compete? PAY -5.8% thanks to its FQ4 miss and light FQ1 guidance.