Look, I'm all for consumer fairness. It would be nice to get better prices. But the fact is, whether you have a 5GB plan or an iPhone unspecified/unlimited plan, your averages are still well within the range of limits experienced by both parties. It hardly makes a difference.
The article is basically making the argument that somehow iPhone users should be punished because they're actually using the service AT&T has been selling everyone for a long time. This is pretty asinine. The real issue here is entirely different and entirely AT&T's prerogative. Let me enlighten you:
AT&T's "3G" network, which is actually 3.5G, HSPA... is on the tail end of its lifespan. The technology in all of these handsets depends on it, of course, but it's done. It's over. There is only one last stage of improvement to GSM tech and it's a stretch as it is. Why would AT&T want to invest in expansion of a dead infrastructure? They don't. They aren't going to any more than they have to. They will expand to the last stage of 3G in the largest markets just as they prepare to roll out the same LTE based networks that every other carrier is supporting.
That said, there's no reason to think bandwidth consumption is the primary concern here. The primary concern is one of density. The number of users each relying on the same cell is too great. It's not a matter of how much data they are transferring on that cell so much as that there must be more cells, or cells must be able to handle more concurrent users. That's just a factor of the proliferation of cellular phones and devices. You can't blame the iPhone for this. It's a problem that would occur eventually anyway as the trend towards data enabled devices existed before anyone even knew about the iPhone. Maybe the iPhone accelerated it, but that is no reason to punish people who like a good user experience.
Of course, there's another concern not addressed and that is the exact same concern that effects cable internet subscribers. Cable internet actually works in a very similar fashion to cellular internet. In the case of cable modems, customers share a download node that has a set maximum bandwidth with its uplink. You are sold rates like 12mbps but there is only a maximum of 60mbps at each node. So if more than 5 people all try to use 12mbps at once you won't get what is promised. However, because most people don't use nearly the maximum pretty much.... ever... the cable companies overprovision the network. They get away with it because the statistics generally match up. However, if you're unlucky enough to live in a neighborhood full of download happy geeks, you're going to hate your internet connection.
The same issue exists in cell towers. A give GSM cell can handle a fixed maximum number of communication slots each functioning as a statically wide band of communication. When a device ramps up from basic voice to data, to higher speed data, it will consume more slots. Or it won't, if there are none available and it will just stay slow or not connect to data, or whatever. So basically if you have 1000 slots on a given tower, and full 7.2mbps hsdpa+ requires 12 of those slots, you can see that there's a fixed number of people who can possibly access the network at full speed. Add to this the already common problem of the actual backing internet connection experiencing the exact same kind of limitation and you can see that infrastructure is a problem of density, not of actual transfer totals.
So, the lesson here is that more uplinks are needed so that uplinks are not as central a point of failure as they are today. What you'll earn is that cells are relatively evenly distributed across all markets but not all markets have an evenly distributed level of usage from consumers. People in metro areas will note the worst performance because there's simply too many people in one place. You'll note the epic failure of networks during large technical conventions with a 1000+ simultaneous attempts at liveblogging the latest digital toaster at CTIA or whatever.
Point is, you can't go blaming a single handset because this same effect can, and will occur without the iPhone involved. If you have convention of blackberry addicts all trying to BBM each other at the same time, in a convention center with 2000 of them all connected to the same cell tower, that's going to give the same bad experience even though the effective throughput is less than dialup internet.