We've gotten to the bottom of the story why Microsoft bans netbook manufacturers from selling machines with 2GB memory. If you want to sell your notebook with Linux then Microsoft won't object, but if you want to sell it with XP, some limitations are imposed.
Microsoft has a special, ultra cheap version of Windows XP for OEMs that is only for Netbooks and this license supports up to 1.5GB memory. It can support more memory, but Microsoft simply won't cover a license and will ask for more money per XP license if you decide to use 2GB or more.
Netbook manufacturers hope that Microsoft will let them use 2GB memory and not pay extra per XP license, but for the time being Microsoft won’t let that happen. So much for freedom of choice.