That’s a bit of a misconception. The iPhone and iPad can both multitask, they just can’t, or more accurately, won’t allow third party apps to run in the background.
Now on the iPhone I understood the reasoning: to protect the core functions of the device, and to keep the battery from getting sucked out of juice in an hour or two.
As for the iPad, those issues aren’t as great. And according to news reports, Apple is going to unveil iPhone OS 4 tomorrow. Speculation is that this upgrade will allow third party apps to run in the background, at least on the iPad, but maybe also on the iPhone. We’ll see.
What I would like to see is wireless data syncs between iPhone and iPad.