A recent study found that consumers are getting more comfortable with mobile shopping, and you best believe that will only continue, as people continue to spend more of their web time on their phones. So as everybody reaches for their mobile devices to make payments, which platforms are they going to use?

PayPal hopes to stay in the drivers seat in this area. WebProNews interviewed Francesco Rovetta, director of business development for PayPal Mobile at SXSW a couple weeks ago, who talked a bit about PayPal’s vision for mobile.

PayPal is certainly not the only player in this space though.

O’Reilly Media Founder Tim O’Reilly has posted a fascinating piece on the "State of the Internet Operating System," which explores in depth, just what the phrase operating system means in the age of the cloud, and the mobile web. While he talks about this with regards to search, media access, communications, identity, advertising, location, and a slew of other categories, one section of this lengthy article talks specifically about payments.

"Payment is another key subsystem of the Internet Operating System," he says. "Companies like Apple that have 150 million credit cards on file and a huge population of users accustomed to using their phones to buy songs, videos, applications, and now ebooks, are going to be in a prime position to turn today’s phone into tomorrow’s wallet. (And as anyone who reaches into a wallet not for payment but for ID knows, payment systems are also powerful, authenticated identity stores – a fact that won’t always be lost on payment providers looking for their lock on a piece of the Internet future.)"

"PayPal obviously plays an important role as an internet payment subsystem that’s already in wide use by developers," he continues. "It operates in 190 countries, in 19 different currencies (not counting in-game micro-currencies) and it has over 185 million accounts. What’s fascinating is the rich developer ecosystem they’ve built around payment – their recent developer conference had over 2000 attendees. Their challenge is to make the transition from the web to mobile."

UPDATE: PayPal contacted me, pointing out errors in O’Reilly’s numbers. "We now have 81 mil active registered accounts and 210 million accounts, in 190 markets and we support 24 currencies."

O’Reilly also mentions Google and Amazon as key players in the mobile payments space, with the Android Market giving Google Checkout a boost, and Amazon having only recently opened theirs up a bit to developers.

Then you have Facebook, who last year started letting users buy physical goods with virtual currency. As business sell more products through Facebook, which is happening more and more, Facebook may play an increasingly bigger role in mobile payments. Mobile Facebook users are usually signed into their accounts all the time.

Which of these payment services do you see yourself using most a year or two from now? Something else? Share your thoughts.