Counterpoint: 3G, let alone LTE, is faster than the home internet that anyone can get at my parents' location, or farther out from it. The wireless ISP here has as much capacity for their whole system as Sprint has for one cell site. Maybe less.
I'm not advocating tethering without Sprint's tethering plan. However there's a company called Millenicom that sells "unlimited" Sprint 3G (50+ GB will get a call from them wondering what's going on). It's $70 per month. There's also Sprint tethering, which I have no remorse on using instead of parents' WiFi. It's $1.70 or so per day (prorated; I remove the feature when I am not using it).
Then there's unlimited data available on my phone, which is faster than what's available (at any price short of bonded T1s) via a traditional ISP. In this case I'll tend to keep WiFi off on my phone (I turn WiFi off when I'm out and about, turning it on only when I know I'll be in an area with a hotspot), pushing web traffic over the cellular network. This is for use on my phone and my phone only...and I'm not slamming the network while doing it...so I figure that this is reasonable behavior.
To put things another way, if you're going to go with the argument that unlimited is only unlimited for those who limit their usage...on a network that has as much capacity as a cable network had four years ago (when Comcast sold service with a 250GB cap), you might as well tell people to go another carrier with a capped plan, since that way they pay for what they use. Less angst for everyone, since apparently my usage on a single cell site dozens of miles away from where anyone else on here lives congests the network for everyone and causes Sprint to kill unlimited data. Oh wait...Millenicom's still around.
Personally, I like T-Mobile's approach to the data dilemma: unlimited on-phone data is $20 per month. That's more expensive than 2GB of data for $10, and less expensive than 5GB of data plus tethering for $30. So obviously T-Mobile has a reasonable expectation that its subscribers to that plan, while not worrying about their wireless usage, will use somewhere between 2GB and 5GB on average. They have this expectation because they've run the numbers and, with their cost structure, they are willing to take the risks associated with offering an unlimited plan...and the rewards (more customers) of doing so. I know a friend whose family switched to the unlimited data plan on multiple lines of service, grabbed a new phone or two,(including his HTC One S) and saved some money in the process. Thing is, they'll continue to be profitable for T-Mobile despite having a fast network, unlimited data and probably very low WiFi usage...
Why do I say very low WiFi usage? Because, for the average Joe, unless they're beaten over the head with WiFi related messages (like many phones do nowadays...if WiFi is turned on), they won't bother connecting to their home wireless network unless the cellular network is too slow for them. Which is fine, because those users (my mom included) aren't doing data-intensive stuff on their phones (500MB of usage per month or so for my mom). Again, it's all a numbers game, and those users are factored in with the numbers.
Also, for what it's worth, if a company doesn't want its subscribers to use a lot of data on their unlimited network, they shouldn't advertise functionality that chews through data. But apparently newer networks can take the bandwidth beating that online video dishes out...which is going to be used mostly away from home anyway, because I'm probably the only one who will curl up with his phone and watch a couple episodes of Dr. Who on it, instead of reaching for a device with a larger screen