The tech industry’s been talking about mobile payments for years, and I find the whole discussion fascinating. Not just the potential and the rhetoric, but the gap that exists between the two. I even spent a year working at a yet-to-launch mobile payments company, BillToMobile. But to be honest, we’re still at least about five years away from seeing mobile payments go mainstream. We’re at “the wind at your back stage,” where the possibilities seem endless, and will soon enter “the wind in your face stage,” where reality kicks in. And on the way from one stage to the other, we’ll see a number of companies fall by the wayside and a few legitimate contenders survive. There is already a long history of road kill in the alternative payment space (PayByTouch, Revolution Money, DigiCash, and PepperCoin to name a few).

So what system for mobile payments will eventually take hold? I’ll get to that in a minute. First, what exactly is a mobile payment?

This is a more complicated question than you think. There are at least half a dozen different definitions. A lot of existing alternative payment companies, entrepreneurs, and VCs are attempting to associate whatever it is they’re doing with the buzz around mobile payments. In my opinion, a real mobile payment is one where the obligation to pay ends up as a line item on your mobile phone bill regardless of the access device or location. However, many would argue that the use of your mobile phone as a proxy for one of your regular credit/debit card accounts or perhaps your prepaid card also qualifies.