When Jobs announced multitasking for iPhone OS 4, everyone got giddy... until Apple said that this important feature wouldn't work in older iThingies because of "hardware limitations". The hardware, however, fully supports multitasking. Why not enable it, then, Apple?
The fact is that the hardware in the old models of the iPhone and the iPod touch fully supports multitasking. By changing a single text line in a preferences file—the property list N82AP.plits—you can enable the new multitasking abilities in the new iPhone OS 4.
So why has Apple decided not to enable it? Most probably it is a matter of resources. The original iPhone, the iPhone 3G, and iPod touch 1st and 2nd generation have a quite slower CPU compared to the 3GS and third generation iPod touch. What is more important: They have a very limited RAM space, only 128 megabytes.
That probably makes multitasking slower than what Steve Jobs and Co. find acceptable. If an user keeps opening applications, it will probably affect the experience so much that many will be unhappy very fast. The question is: Shouldn't be this an option available in the system preferences? Most probably, Apple thought the benefits will never be enough even for advanced users, and the feature would confuse and frustrate normal consumers, opening a potential customer support nightmare.