I've just e-mailed the following to Amazon, let's see what they reply with:

Hello,

I have pre-ordered the Nokia N900 on Oct 17th. I've noticed that a rebate offer came out a few days ogo for $50. I've also noticed that one of the requirements for that rebate offer is that the purchase be made between Nov. 16th and Dec. 31st 2009.

Although I have pre-ordered the device on October 17th, I have not in fact purchased it yet.

I just wanted to ask and make sure that the invoice I will be receiving from you will show the actual Purchase date of the device. Meaning the date you will charge my Credit Card.

I also need this "actual" date to be reflected for the purpose of taking advantage of my square trade warranty. The Warranty is effective as of the purchase date, so I do not intend to pay for a warranty that will cover me from the day I pre-ordered, without having had a device in my hands for over a month.

Thank you very much for your time and your services.

Sincerely,