While iOS and the App Store generally do a pretty good of keeping your apps up to date, even going so far as to transparently update them in the background with iOS 7, we’ve noticed that in some cases an update may not install properly, resulting in unpredictable behavior. In its most innocuous form, an app may appear to have updated according to the App Store, but still look like the old version; in more serious cases, you may be faced with an incomplete update that causes the app to crash or exhibit other odd behavior. Even worse, when this happens with apps that are allowed to run in the background—like Facebook—it can actually bring your entire iPhone, iPad, or iPod touch to its knees.
If you’re experiencing something odd with a specific app that has been recently updated, the obvious solution is usually just to delete it and reinstall it from scratch. Further, if your iPhone or other iOS device has started behaving oddly in general—poor battery life, lags, or even freezes—look for apps with background privileges. VoIP apps such as Skype are common apps that get special privileges to run in the background, and it’s worth noting that Facebook officially became a VoIP app earlier this year and was granted the same privileges to potentially run amuck even when it hasn’t been opened.
Keep in mind, however, that unless an app stores its data in iCloud or its own cloud service, you will lose any data in the app by removing and reinstalling it. If your data is crucial, you may need to revert to an older iTunes or iCloud backup instead, although this will mean restoring your entire device from scratch.