TiPb just received a tip from inside one of Apple's carrier partners on the memo reproduced below. We can't verify it but are running it just in case anyone notices any problems and comes looking for potential causes.

Our tipster thought Apple might be using the downtime to prep for some iPhone 3.0 and next-generation iPhone hardware goodness. We have no way of verifying that either, of course, but with under 10 days to WWDC 2009, nothing -- fact or fiction -- surprises us anymore...

On Sunday evening May 31 / Monday June 1, in some time zones Apple will perform maintenance on the servers responsible for all iPhone activations.

This is a planned maintenance that begins at 8:00 p.m. and ends at 11:00 p.m., United States Pacific time.

During the scheduled downtime, attempts to activate a new iPhone will result in iTunes displaying a message that says activations are currently unavailable.

If a customer reports this as a problem please explain that:

Nothing is wrong with iTunes or the customer's iPhone.

This is a scheduled downtime for system maintenance.

The iTunes Store, App Store, MobieMe, and www.apple.com are not affected.

Per the message in iTunes, the customer should try connecting again after the maintenance period has ended."