It’s tempting to blame — as many headline writers have — Apple’s (AAPL) newest iPhone and its voice-activated personal assistant for the fact that 3% of mobile users now consume 70% of the world’s bandwidth, up from 40% in 2009.

After all, the iPhone 4S with Siri consumes nearly twice as much data as the iPhone 4 and nearly three times as much as the iPhone 3GS, according to a report issued Friday by Arieso, a British company that advises mobile operators in the U.S., Europe and Africa.

Even Michael Flanagan, Arieso’s chief technology officer, seems to lay the widening bandwidth gap at Siri’s door.

“I use the iPhone 4 myself and when I first heard of the iPhone 4S features I was not compelled to rush out and get one,” he told Reuters. “However, the data usage numbers I am seeing make me wonder what I am missing.”

But as Flanagan’s own study shows, it’s not the iPhone 4S that is jamming the world’s cellular airwaves.

“The hungriest 1% of all subscribers,” who consume 50% of the world’s bandwidth, according to Arieso, “were predominantly using USB dongles or 3G Modems.” Quoting from the full report:

As noted in earlier studies, 3G modems are generally noteworthy for two aspects: 1) their relatively low volumes of subscribers (compared to smartphones and other devices) and 2) their remarkably high volumes of data per subscriber. The product of these two items results in the aggregate data volume across all 3G modems and is typically competitive with (and sometimes in excess of) the aggregate data volume across all smartphones. Table 1 shows a considerable 23-to-24 times increase in the data volume per 3G modem subscriber over the iPhone 3G reference. This is achieved by making nearly one-seventh the number of data calls per subscriber.

In other words, if you need someone to blame, don’t point your finger at those crazy people talking to their iPhones. Worry about the kids with dongles streaming movies to their laptops.

You can read Arieso’s press release here. The full report is available upon request.