With each new iteration of Apple's iPhone, we expect to see the addition of new features like speedier processors and better cameras. What isn't necessarily expected is that each subsequent device will consume way more data than its predecessor. But, in fact, this is the case.

The iPhone 4S uses about twice as much data as the iPhone 4 and three times the data than the iPhone 3G, according to a new study by Arieso. What causes the 4S to hog so much data? Just ask Siri.

Every time you tap the button and ask Siri a question, it eats up about 63 KB on average, according to detailed testing done by Ars Technica. Sure, that's a modest amount of data, but if you use Siri frequently, it adds up over the course of a week.

Even local tasks like setting an alarm or adding a reminder use some data, since Siri bounces requests off of Apple's servers before executing them. Naturally, those types of queries take up less data. More Web-reliant requests like searches can use closer to 100 KB apiece. At the end of the month, it may not be enough to blow your data cap to smithereens, but it can add a good dozen or two megabytes.

The news that our smartphones are getting more data hungry comes at an inconvenient time, just as carriers are getting less generous about doling out those bytes. Sprint is now the only carrier offering unlimited data for smartphone users, and even that plan reportedly has its limitations. As smartphone usage has exploded, charging customers based on their data usage has become a way to both maximize revenue and keep congested networks under some control.

Regardless of the handset, data usage in general has been on the rise for the last few years thanks to the proliferation of devices, popularity of video and our increasing propensity to keep our digital stuff stored in the cloud.