Google’s mobile wallet appears to be staggering to the finish line of 2012. After all, it was a year that started with a reported security breach and is ending with speculation that the search-engine giant will add a plastic card to the otherwise entirely digital wallet.

The Google Wallet we see today is a much different product from what we had a year ago. Here are the major changes that took place this year, and the challenges Google faced — and still faces today.

Twitter's immense popularity has caught the attention of many established payment companies and entrepreneurs. Several have attempted to turn the microblogging service into a payment channel, but so far there are few success stories.

Apple introduced its Passbook app — a wallet that stores other mobile wallets — alongside the iPhone 5 in September. Three months later, has Passbook revolutionized mobile payments? Or is it starving from lack of support?

At the heart of many mobile wallets is a system for offering discounts, so these wallets seemed a natural fit for Black Friday shopping. Did they live up to their potential?

This holiday season many retailers are introducing experimental payment technology — but will shoppers, stressed and desperate, find benefit in these experiences or stick to methods they know?

SCVNGR's LevelUp is targeting a broader audience for its mobile-payment system by working with the prepaid card marketer NetSpend. The partnership represents new territory for both companies.

There is no single definition of a “mobile wallet.” Each product differs vastly in its choice of technology, audience and the basic type of payment upon which it was built — but most fit into a few simple categories.

Google has reinvented its mobile wallet a few times, and its latest reinvention, a rumored plastic card, raises questions about the mobile-pay product’s direction.

Many third-party mobile payment providers, such as Google and Isis, are seeking bank partners for their mobile wallets. Should banks agree to their terms or go it alone?

MasterCard's approach to mobile payments is driven greatly by the series of mobile phone innovations simultaneously occurring around the world, according to the network's group executive for mobile.

If mobile payments can be presented as an opportunity for merchants and point of sale developers, rather than a disruptive threat, the attitude will speed adoption and provide consumers with a better experience, according to Matt Cicciari of Merchant Warehouse.

Any uncertainty in mobile wallet development fuels speculation in an industry anxious to see what shape mobile commerce will ultimately take. In this industry, products that make it even farther than where Isis is today don't always work out.

Many in the industry are starting to catch on to the concept that payments, while a critical foundation for mobile wallets, are taking a back seat to the sexier consumer-facing digital coupons, loyalty programs or targeted promotions through a mobile phone.

The LevelUp mobile payment system, best known for providing free incentives to consumers and free payment processing to merchants, picked up 4,000 merchants and 300,000 end users since its July 2011 inception. But with so much being given away for free, is there a future for the startup once its new clients become regulars?

Braintree says its vision for the future of e-commerce received a significant boost when the online and mobile payments provider lured a Google Inc. executive into its fold last month.

PayPal was an early supporter of Bump, whose technology could simulate an NFC payment by moving money when users' phones sensed they were being tapped together. But PayPal dropped Bump from its mobile app this year. Where does this leave Bump?

As new mobile-wallet systems appear and old ones fade, many are asking who will win the “mobile wallet wars.” According to the mobile-pay venture Isis, there may never be a clear winner.

Everyone seems to want the success that Square has in the mobile payments marketplace, and Amazon appears to be the next in line to join the device fray.

Mobile wallets promise simpler payments, but the road to get there has been bumpy and, quite often, bizarre.