This is a legitimate concern for me, but almost no part of my mother's life takes place online. She did have a mac, but lost that and there is no money for a new one. She also has an android phone, so the privacy argument applies here as well and is still very valid. Eventually I will get her on a mac or ubuntu laptop or something like that.

In terms of usability I have to tip my hat to Google. ChromeOS is very easy to use so far. Probably until chromebook vendors start adding all sorts of their own shitty tools and accounts like Huawei has done with their phones.