In his article, Why the iPad and iPhone don’t Support Multitasking, Robert Love says:
Apple says they do not support multitasking because it is a hamper to stability and a drain on battery life. That clearly isn’t true—the iPad has plenty of processing power and battery capacity.
Two words Robert: legacy devices. While the iPad and iPhone 3GS both have sufficient CPU to handle multitasking, neither the original iPhone nor the 3G does. I am reminded of this every time I use a 3G. Further, while the iPad seems to have plenty of battery life, that is a word very few people use to describe the battery life of any touchscreen phone.
Rumor is that Apple is going to add multitasking in a future OS release. This rumor likely is true. Is Apple somehow going to make background applications not consume any battery? Of course not. These excuses are straw men.
Except that’s almost exactly what Apple did. They provided application developers with the utility of background processing, but without the egregious consequences. Not surprisingly, multitasking only works on the current generation of iPhone OS devices.
The real reason that the iPad and iPhone do not allow third-party applications to multitask is likely more complex, more technical. …
I believe the rest of Robert’s argument is spot on. Where I differ with Robert is that he thinks the CPU and battery life are straw men. I believe they are very real issues that Apple has to contend with.