One often-mentioned criticism of the iPhone, despite how the device and the information infrastructure in which it exists forced all the primary mobile carriers and manufacturers to produce and support touch-phones that are handheld computers/communication devices, is how it does not multitask.
I think it does multitask, though.
I have not read any official Apple specs about the iPhone and how it does not multitask, but I have never seen anyone say that it does, or that the critics are wrong. But if you have one, you can try this (and there are probably some other things you could do to get a similar thing to happen).
If you are in the photo app, you can choose to send a photo via text or email. If you choose email, the iPhone's email header with the to: and cc: and subject: fields comes up, you can auto-fill the to: field just like in email--basically it looks like you are in the email app and are sending an email with a photo in it, because you are. (I am not sure to what extent, though. It may just be "creating" an email, so it may not check for new mail.)
When you hit "send", you are taken back to the photo in the photo app. If the iPhone had no multitasking, your email would stop sending at this point. But it doesn't. It is being sent, from email, while you are in the photo app. It is multitasking.
If, when you hit send and then are taken back to the photo app, you switch over to the email app, you will see the "send" progress bar and see that it is making progress, but that it had started before you opened up email. Speed varies depending on the network, of course (wifi, 3G, reception, etc.).
There may be some reason this is not referred to as multitasking, but, to me it seems that it is indeed multitasking. I am in one app (the photo app) while another one is working in the background (the email app).
(See also my Reviewers are Pointless post about how it is easy to switch between apps on the iPhone where you don't have the screen real estate to see more than one app running in any large way anyway--sure you could fill your screen with ten status bars, but I don't see the point to that--so although it is not multitasking in this example, it is usually like suspending an app that you may not be doing anything with anyway, although there are some apps you might want running.)
EDIT: I asked a knowledgeable person about it, and he said that multitasking works but only for Apple applications. So, yes, but not for your app, so some people feel the answer is no. But yes. Irrelevant now, but I would have preferred accurate information in the first place.