Apparently Sony feels that the ability to download digital content is very important to US consumers and would rather emphasize the 250GB & 500GB sizes. They also believe that consumers would rather buy a new PS3, rather than change the hard drive in their existing PS3.
Personally I don't agree with this strategy. I'm sure that there is a significant segment that doesn't download content or put their PS3s online, also I am sure some consumers would like to purchase a bare bones PS3 so they can add in their own HDD or purchase an even bigger HDD. This could have been a good opportunity for Sony to be able to sell a PS3 for $200 in the US...
I am even more confident now that the flash memory version will eventually come to the US. The official Sony press release specifically states "a newly added 12GB flash memory model initially for Europe only."
Hope you are right, I was going to go out and buy that specific model when it was available. Do we know that we can put and HDD in it for sure?
Yes you can.
"the new PS3 with 12GB flash memory offers opportunities to experience the world of PlayStation® at an affordable price point. Users can also expand the storage capacity of the 12GB flash memory PS3 by connecting a dedicated HDD (250GB) to be released concurrently with the new model*5."