AT&T has justified its throttling rules for unlimited-plan customers by saying it was only targeting its top 5 percent of bandwidth users. Validas, a company that steps consumers through choosing data plans, examined over 55,000 cell phone bills from 2011 that consumers provided from their various carriers. It found that the top 5 percent of AT&T's unlimited-data customers targeted for throttling aren't the data hogs AT&T is making them out to be.

AT&T has said it would throttle, or slow down the data traffic speed, for any unlimited plan holder who uses more than 2GB per month. That's supposed to only affect the heaviest, top 5 percent of data users on unlimited plans, not those with tiered plans, which are now the only kind available to new customers.

Suspected data hogs didn't use actually use so much bandwidth.

The Validas study reveals that the top 5 percent of bandwidth users on AT&T's unlimited data plans use an average of 3.97GB per month--hardly the kind of numbers that would choke AT&T's network. There is also little difference between 3.97GB and 3.19GB, the average among AT&T's top 5 percent tiered-plan users.

Validas estimates for free what you could save on your cell phone bill, and charges for a report that shows which plan you’d need to purchase to get the savings. Since it makes its money from consumers and not the telecommunications companies, Validas doesn’t appear to have a financial interest in skewing its study toward a particular carrier.

In a blog post, Validas concludes that throttling isn't being put in place to curb greedy data hogs, but rather to migrate users of traditional unlimited plans to tiered plans. These plans are far easier for AT&T to manage and don't pose threats to its network.

If AT&T can produce an independent, third-party study that proves its throttling measures target only a minority of bandwidth-sucking users, the case would be effectively closed. If it can't, it should stop throttling unlimited-plan users who use under 4GB of data per month, or introduce something equivalent to the transparent throttling that T-Mobile has established for customers who use over 5GB per month. Standard business-only usage, such as email and the transmission of most graphic files, is not going to add up to the average numbers that unlimited data-plan users are polling with Validas.

You can find out if your service is being throttled using a tool called Glasnost, which examines different modes of data transfer.

AT&T has grandfathered in smartphone plans that are supposed to offer unlimited data transfers per month for $30. At the other end of the spectrum, the AT&T Data Plus plan charges casual smartphone-only users $20 a month for 300MB or less