Seems this is no longer isolated to South Africa. This time it's AT&T implementing it. They are also being very strict about wireless data usage.
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Article
Trang's iPhone was throttled just two weeks into his billing cycle, after he'd consumed 2.3 gigabytes of data. He pays $30 per month for "unlimited" data. Meanwhile, Dallas-based AT&T now sells a limited, or "tiered," plan that provides 3 gigabytes of data for the same price.