Apparently the $30 plan is a "Walmart Plan", just that you can get it from the Internet. If you look at Walmart's website, it adds the tag "Only at Walmart" to the $30 plan. My guess is that it is supposed to be a Walmart only plan, just that they had to have an Internet option for those that order from Walmart.com or didn't want to activate the phone in the store, which makes it available to people like us.
Personally, I ordered the Activation Kit online (for 99 cents) and tried activating online. In my case, I had trouble with the online activation and had to call. While it was simple, if longer than I would have liked, to activate online, I did need a supervisor to actually add me on the $30 plan, since it is not something they offer over the phone.
I also went into a T-Mobile store before signing up, to check on coverage and speeds in my area. I found it rather funny because, since I told them I was looking at prepaid with the Nexus, I could tell they wanted to tell me about the Walmart plan but weren't supposed to (since they can't offer it). They seemed relieved when I brought the plan up and said that was my plan. In any case, the T-Mobile reps I've talked to all seem to call it the Walmart plan.
From what I can tell, the rumor that people have to pay for their plan at Walmart is false. My best guess is that employees are coached to tell their Walmart plan customers that they should buy a $30 prepaid T-Mobile card each month from Walmart. I'm sure some employees have misunderstood, and end up telling customers that they have to pay by buying the cards from Walmart.
