Microsoft has had some very odd restrictions on netbooks that most of us have been unaware of. The first one that was really made public was the hard drive size limitation, which was originally capped at a mere 80GB. This may have not mattered to most early netbooks where storage capacity could be in the sub-32GB range, but newer models are quickly approaching that. Microsoft responded by raising the cap to 160GB - much friendlier, but still you must question why they impose that limit in the first place.
Another limit that Microsoft has in place is a hard limit on the amount of RAM you can have in a "Netbook", or more specifically how much RAM the "netbook" edition of Windows will tolerate. In this case, it'll allow an absolute maximum of 1GB. You might think that's plenty for a "Netbook" - but we all know that the hardware demands of systems change rapidly, and when a "netbook" version of Vista is released I am sure it'll be anything but RAM-friendly.
Microsoft could change this restriction in the future, but why have it in the first place? In today's world, 1GB of RAM is really not that much. Even a desktop user with an office suite, an IM app, a few minor programs and content-laden web pages can push themselves up to the wall with a mere 1GB available.