When the SDK came out I was bemused to find similarities to the Palm OS world: No multitasking, data access limited to the application's data.
Since then we've learned that Apple's applications do multitask (if I actually owned an iPhone  I'd have noted that obvious fact, but I write these posts very quickly) and some iPhone partners (AOL, ?Adobe) will be allowed access to multitasking. For most developers though, developing for the iPhone OS X is rather like developing for Palm OS .
Fubo.org has made a persuasive case over the past few days that these are justified and measured constraints given the current state of iPhone development. The articles are well worth reading, but I particularly liked the fine way he concluded his last post:
...If you’re still unconvinced, let me ask you one final question: do you want to get IM notifications while you’re making a 911 call?
 One developer I read noted that the original Palm OS SDK had a more sophisticated 'wake me when an event matches my entry on the event registration queue' function than he found in the current iPhone SDK.