UPDATE [Tuesday, January 17. 2012 at 2:29pm ET]: An AT&T spokesperson chimed in with a comment noting that “throttling only applies to top users with grandfathered unlimited plans”. The full quote is included at the article bottom.
AT&T and other major carriers in the United States recently instituted data throttling and began limiting network speeds for the top 5 percent of data-hungry users. Carriers around the world tend to hide data throttling in fine print, so users are in for a surprise when they find out that their unlimited plan entails data throttling once a carrier-imposed ceiling is reached (usually 1GB per month). Throttling is not something worth losing sleep over until it hits you. For starters, throttling reduces your downlink speed by a factor of 10 or more. Depending on your carrier’s network, this means your throttled downlink will drop all the way down to a paltry 0.1MBps. What you might not have known is how badly throttling affects the user experience on your device…
As a rule of thumb, bandwidth throttling limits your cellular connectivity to EDGE radio technology. EDGE was acceptable when the original iPhone debuted back in 2007, but today it no longer suffices. As you can see in the above clip put together by AppAdvice, EDGE drawbacks include long connection times, super-slow data transfer speeds and the weaker digital signal —to name a few. All of these factors degrade your user experience, as websites load super slow and the entire device feels sluggish. This is especially the case with many Push Notifications enabled and iCloud data syncing taking place. Yes, you should care if you are being throttled, because it is a death sentence to your mobile lifestyle.
UPDATE: An AT&T spokesperson has provided 9to5Mac with the following clarification:
For AT&T, throttling only applies to top users with grandfathered unlimited plans. As we said last summer, smartphone customers with unlimited data plans may experience reduced speeds once their usage puts them in the top five percent of our heaviest data users. We will continue to send reminders and communicate with these customers ahead of time as their usage approaches the top five percent.