wifi sync of iphone seems so logical to end users but I think apple doesn't see it that way.
When I first got my iphone, I synced to activate it and than I assumed everything was going to synch with my iphone and macbook. Than I realized wait contacts/calendar is not synching. When I realized I had to connect iphone with USB cable to synch, it was a mild shock to me.
But I think I can see apple's reasoning for not coming up with wifi synch.
1. battery. when you synch with usb, it's faster than wifi and it charges at same time. iphone battery discharges fast already so using wifi will only speed up draining the battery. Can you imagine copying a few gigs of video over wifi? Image how long it will take and how much battery will be used up in the process.
2. mobileme. I actually agonized over this. Did I really want to spend $100 a year AFTER spending $$ for iphone/case/apps/warranty? The cost is quickly adding up to match cost for decent laptop. Once I gave in and got it, I can see it's useful. I can keep OmniFocus synchronized easily over iphone/macs. I can save files there and edit directly using word/excel, unlike docs.google.com. But you notice that you can't synch mp3/movies over mobileme. They don't do video synch via mobileme due to wan speed and licensing issue. But one less obvious but practical reason is file copy speed. It may work but it will tax the network and hence give impression to end user that it's not intuitive, perfect, smooth. Not an image apple wants to give.
BUT, I think apple should still include wifi synch of contact, calendar, and other stuff that's not heavy. Apple should realize not everyone is going to sign up with mobileme and than people HATE having to plug in/out cables. We are already drowning in cables.