According to Apple Multi-Tasking do not work on 3G, but it looks like Apple choose to turn it on due to slower chip on the 3G. So enabling Multi-Tasking on a 3G will slow the 3G down so to avoid this issue Apple just turned it completely off on the 3G offcourse this is done to avoid 1000′s of calls and to keep their Product running Efficintly. But if a user wants to enable Multi-Tasking on a 3G iPhone it can be done fairly easily , as easy as turning a Tag Value to True in a .plist file This is according to cdevwill.