UPDATE: The iTweakiOS blog accusing Apple of throttling data speeds has been removed, and Kevin Fitchard of GIGaom has debunked the rumor.
Joseph Brown from iTweakiOS, the developers behind the T-Mobile, AT&T and Sprint carrier hacks, claims Apple is working with wireless carriers to slow down the data speeds of certain iOS devices. In a very detailed and long blog post, Brown explains why iPhones are being "out-performed by Android devices," and why he thinks his recent carrier hacks have been able to deliver increased data speeds. Brown says both "Apple and the carriers have implemented coding to purposely slow down or limit the data speeds" a device can achieve.
Brown posted several examples of "throttle coding" (pictured above) from AT&T, Verizon and Sprint, while noting "T-Mobile is the exception" to the throttling accusation. Brown doesn't claim to know why Apple and the carriers are limiting data speeds, he just says they are.
No one has really confirmed or denied if Brown's carrier hacks actually increase your iPhone data speeds, or if his latest claim of iPhone throttling is true. You can read his entire explanation and see his evidence on the official iTweakiOS blog, and decide for yourself.