Though its shares — and back when it was a part of eBay , eBay’s shares — have dipped a number of times on news that a tech giant is trying to muscle in on its turf, the company has kept delivering 20%-plus payment volume growth like clockwork. But while any talk of a would-be “PayPal-killer” merits skepticism, the company does arguably face a tougher competitive environment than any time in recent history.