The limit set by ATT used to be 20 or 25mb for an app download. Then over a year ago, that limit was updated to 50mb. Apple was just able to increase it to 100mb recently, but Microsoft has not been able to do so. It may just be the pull that Apple has with ATT that they got priority treatment, or that it requires a software update, in which case wp could get it in 8.1! But at the moment the app limit is 50mb for windows phones on ATT.
