Sonny Dickson recently discovered another hidden feature in iOS 5. The ability to enable Youtube HD video playback on 3G can now be turned on thanks to the find. The hack is simple and similar to other finds like the panorama feature.
You can follow his instructions to enable on your device
1. Download iBackupBot
2. Backup your iPhone/iPod in iTunes
3. Open iBackupBot and find the backup, then load it.
4. Find Library/Preferences/com.apple.youtubeframework.plist and open the file. (if your software isn’t registered you’ll have to press cancel and then it will open)
5. Add in the following code: <key>HD3G</key><true/>
6. Save your modifications, and then restore from backup from within iBackupbot.