As slashdotters love car analogies, I'll start with one. A car is a rather complex device, and yet every day millions of joe sixpacks are driving it around, more or less safely. Why? Several reasons, but the two most important ones are:
* the interface has been dumbed down tremendously
* you do not (in general) maintain it yourself
These two points have made it possible for every day people to drive a car without knowing the science behind it. Microsoft has been trying for years to do the same with windows, to dumb down the interface to the point that average users can not only use it, but to a certain degree maintain it.
However, the latter is simply impossible in my opinion. Computers are too complex to be dumbed down enough for joe sixpack, however chrome OS offers a nice solution. They simply give you an interface, but they relieve you of the maintenance. No longer will you be burdened with deciding whether or not clicking "ok" is going to crash your pc, no longer will you have to wonder whether renaming that "wav" file to "mp3" will actually work. They do the hard work, they maintain it and they offer you an interface that is easy enough for everyone to understand.
Note: i'm a linux-only kind of guy, so chrome os is NOT for me, but i can see the appeal for all those family members that keep pestering me cause they got the latest fashionable virus