Just noticed something today which is a bit odd.  I had a few heavier books that were sent media mail and below the City State Zip and price is this:

"The timeliness of service to destinations outside the contiguous US may be affected by the limited availability of transportation".

This is underneath every single item sent via Media Mail.  A bit repetitive and unnecessary it seems but I guess they want to make sure everyone knows that Alaska, Hawaii and others are on the slow boat.  Definitely need to be sending those with PBS DC as I'm sure they'll go lost before received.

Media mail is the lowest priority and sent on a space available basis. So any place that requires a boat or airplane for goods is going to take longer because they load up the Priority and First Class mail first.

Yes, Media Mail to Alaska, Hawaii, and Puerto Rico frequenly arrive near or after the 'lost' date.  Sending these books DC is probably appreciated by PBS members in those locations, and allows them to check on books traveling to them 

Living in HI, I can definitely say that Media Mail can take anything from days to 7 weeks.  I've had books arrive to me within days of leaving the east coast and others that have taken weeks and the same with those I've sent.

In the beginning I used DC all the time.  Now, I only use DC when sending more than 1 book.   I always PM the member with the DC (if applicable) letting them know that it can take up to 6 weeks for their books to arrive and that often nothing shows up on the scan until the package gets to Richmond, CA via slow boat across the Pacific.  Members seem to appreciate this.  But I have sold items on eBay and the buyers want the cheapest shipping option but are not happy that the transit time is soooo long.

Many of my books get marked 'Lost' but so far none have been 'Lost' forever.

I mailed a PBS book to Guam yesterday.  Bought DC and postage through the PBS system; nevertheless, I took it to the postal window and  asked the postal clerk to be sure to scan the DC.   In the process,  up popped on the machine:   Fill out a customs form   So I did and it went on its way.

Is it routine to fill out a customs form for mail going to Guam?

Came home and noticed this comment under the book I sent:

Because this book is coming from or going to an address outside the contiguous US, it may take longer than usual to arrive.
USPS estimates arrival before 1/15/2010
Date of system action: 1/16/2010 12:00 AM ET
Please do not contact us before this date.

Guam is part of the US, don't know why you had to fill out a customs form.

The DMM says:

2.4 Customs Forms Required

2.4.1 Priority Mail Weighing 16 Ounces or More

[11-2-09] Regardless of contents, all Priority Mail weighing 16 ounces or more sent from the United States to ZIP Codes 96910-44, 96950-52, 96960, 96970, and 96799, and all Priority Mail sent from these ZIP Codes to the United States, must bear customs Form 2976-A. If Form 2976-A will not fit on the address side of the mailpiece, Form 2976 must be used. This mail must be presented to an employee at a Post Office, to a letter carrier when using Click-N-Ship with Carrier Pickup, or to a Postal Service employee designated by the postmaster.

If you're mailing Media Mail rather than Priority Mail, then I don't see why this would apply.  Hmmm.......

It's repetitive under each transaction on the receipt because the POS system is programed to add that to each media mail transaction.  Why?  Probably easier and faster then programing an extremely outdated, slow, very small hard drive, minimal memory system to track how many of each type of transaction for the receipt printing job in the program.  Simple if-then-else logic.

Guam is outside of U. S. customs, setting and enforcing its own rules. Coming from Guam to the States goods would need a declaration also.