Well, I just received an email reply from Samsung to the question 667Mhz/800Mhz, and they said to check with Crucial Memory. Crucial is now recommending PC2 6400 (800Mhz).
http://www.crucial.com/store/listparts.aspx?model=NC10-14G
So then I did an online chat with a Crucial tech:
Welcome to Crucial Technology’s Expert Online. An Expert Online agent will join you in a moment… Please do not begin typing until you have been connected to an agent.
Hello, my name is Dan . How may I help you?
Riffraff: Hello, I am getting a Samsung NC10, and Samsung said 667Mhz memory is ok, but your website says 800Mhz.
Dan : Do you have the 14G version?
Riffraff: Yes. The Samsung specs say 800Mhz, but my understanding is the Intel Atom proccessor (or chipset) only supports to 667Mhz memory.
Dan : I show that for this system the PC2 6400 is guaranteed compatible.
Riffraff: And that is 800Mhz, correct?
Dan : Correct.
Riffraff: Cool. This is new. I think your website said PC2 5300 until very recently
Dan : After we have tested for ourselves we do update the site.
Riffraff: Thanks for your help
Dan : You’re welcome. It was my pleasure to help, and I hope you were delighted with my service today. Thank you for visiting Crucial.com. Have a wonderful day.