With the debut of iOS 7, Apple now allows app downloads of up to 100MB over cellular connections. If the app is larger, the user is prompted to connect to Wi-Fi.
Apple previously boosted the limit to 50MB with the launch of the third-generation iPad in March 2012. Before that, users could only download 20MB apps over a cellular connection.
Developers usually try to keep their apps below the cellular download limit, as they believe by going over that limit, they reduce the number of purchases users make on a whim.
Make sure to check out our full iOS 7 coverage roundup for all the details regarding iOS 7, and all of our iOS 7 launch coverage!