This doesn't make sense from a bunch of different perspectives.
Yes, with the Chrome computers, you might not get viruses. But that would be the same as if you got any Linux Netbook that they sell, and would still have many more features than the Chromebook.
You also bring out a lot of anti-features with the Chromebook as well. When you give this to your parents, and they ask where their little blue "E" is, or where their Spider Solitaire is, what will you say? What about those students and businesses that require to have certain software on their system, that the Chromebook doesn't support? Suddenly you exchange technical problems like getting rid of viruses with explaining how to do things in a new environment, with new rules.
And at the end of the day, is it worth it? For me, I'd rather take that $450 dollars (or $350) and buy a fully functional PC that can run all my favorite software and also get me access to the web.
That is not to say, however, that I would not buy one in the future. If they brought the cost down ($150 would be almost an instant buy for me), and/or had a fully matured "app" store if you will, I would probably change my mind. But I look at it, and the only key features I see are the great battery life, and free 100MB 3G access a month, and a whole lot of negatives and unanswered questions (Are they going to have bad customer service like they did with the Nexus? Are they going to give up on this like the Wave, or keep pushing it?)