The Google Translate API has been officially deprecated as of May 26, 2011. Due to the substantial economic burden caused by extensive abuse, the number of requests you may make per day will be limited and the API will be shut off completely on December 1, 2011.
I hope you didn’t build a business depending on this free API that was completely out of your control.
Nearly every free or inexpensive iPhone translation app is just an interface to this. You can tell whether an app uses this by whether it works offline: Google Translate API apps, obviously, can’t. (They’re not very useful for international travelers who don’t use expensive data-roaming plans.)
I wonder how Google felt about all of these iPhones hitting their free translator constantly. Seems like the kind of service that they might want to be exclusive to Android. Maybe iPhone apps are the “abuse” they’re talking about.
These apps will probably just switch to the Bing Translation API. Microsoft loves losing money with online services, so this should stay free forever… unless they get a new CEO who isn’t crazy about pouring billions into a hole. And if that happens, these apps are going to be in trouble, because I don’t know of any other free translation APIs.