Apple has increased the over-the-air download size limit for the App Store to 50MB, from the previous 20MB. This only makes sense with cellular data networks getting faster speeds, especially with the launch of the new iPad, its Retina Display and 4G LTE data networks. The new iPad's Retina Display will require its apps to have larger file sizes, thus the increase in download limits. This means that any app that is 50MB or less can be downloaded over the 3G or 4G networks.
The 50MB limit is now in effect, and applies to all kinds of media – music, video and apps. Now if the cellular companies would bring back "real" unlimited data plans!