But until it's essentially universal, that still shifts burden to the user: they have to look around and try to figure out whether this alternative payment method is accepted at this merchant. Why wouldn't they just whip out their credit card that they know is going to be accepted?

EDIT: What I mean to say is: if credit-card-swiping were particularly onerous, I could see this easily taking off. But since it's not (at all!) and people are trying to replace it with something that seems equally-if-not-more burdensome, it's hard for me to see why this would catch on outside tech folks that mostly do it for the geekfactor.

There are a few killer features that come to mind (though I'm not sure if Google is already looking at them):

- no paper receipts. Do I want my receipts? In an ideal world, of course, but in real-life that just means more paper junk. Receipts are also awfully easy to lose - making returns onerous. Imagine having an electronic receipt instead of juggling all of that paper!

- doubling up on loyalty cards and payment. Instead of swiping a loyalty card once, and then again for actual payment, a NFC transaction can potentially do both at once. This also reduces the number of cards I have to carry around dramatically. Bonus points if they can make this work with my library card (with the added bonus: if I'm late returning a book, they can just charge me).

- more fine-grained budgeting. Right now Mint knows if I spent $50 at Staples. It doesn't know what, though. An itemized electronic transaction record would tell my budgeting software that the $50 was spent on printer ink, instead of, say, a new gadget.

- immediate feedback without extensive POS modification. I've noticed some grocery store checkouts now have a secondary printer that spits out special offers to you (assuming you scan your frequent shopper card). This can be expanded upon greatly without modifying POS hardware - i.e., pushing promotions directly to your phone.

I don't know if I'm like most people in this regard, but I'll carry my phone with little issues but I'd prefer to carry as little plastic in my wallet as possible. If I had an NFC phone and this service was available where I live, I'd be removing my Paypass Mastercard from my wallet the moment I got home.

I think the problem they're approaching is having too many cards like loyalty cards and such. That's a real problem unlike swiping any card.

In terms of usability, the one-tap pay systems that are rolling out (certainly in the UK) for low value transactions (no PIN or signature required) with bank-issued debit/credit cards is a huge leap forward with respect of speed of transaction.

There are too many loyalty cards. I usually won't sign up for them unless it's for a store I go to all the time, because I don't want to carry them around. I'll carry one for the grocery store, but not places I only go to occasionally like Walgreens or Best Buy. With Google Wallet you won't need to carry them, so they won't be as much of a burden, so you can have more of them. Merchants will like this and consumers will too.

I worked for ViVOtech (one of the biggest PayPass Point of Sale vendors) back in 2003; it is always surprising to me how widely deployed the readers seem to be, and how little actual use there is, even today.

Something like this could go a long way toward adoption, but I'd be a bit concerned that RFID/NFC might be bypassed by cheap CCD/CMOS.