Ah well, I went ahead and bought 800Mhz memory today. Not an issue though as the price was the same for 667Mhz ram too.
EDIT: I checked my order and decided to cancel it as it was still pending. Bought 667mHz ram instead along with the LG GSA-E50L external DVD drive from Elara.
Well, I just received an email reply from Samsung to the same question, and they said to check with Crucial Memory. Crucial is now recommending PC2 6400 (800Mhz).
So 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.
With regard to 800Mhz ram. As far as I have read online, 800Mhz ram will work on an NC10, but the system will only run it at 667Mhz. The above discussion only confirms this fact. Dan, from Crucial, did not state that the 800Mhz ram would actually run at 800Mhz, only that it would work with the NC10; which will probably mean running at 667Mhz.