The difference with Google is that millions of consumers and businesses are simply forced to buy Windows because that is the only way to run software that they need. There is pretty much nothing you can run on ChromeOS that you can't run outside ChromeOS almost just as easily, including all the related Google services if you want them. Thus people buying it are buying it on its own merits and people using Google services related to it are using those on their own merits.

I think the bigger case against Google on this front is with how they are tying Google+ to Google Search. I am actually kind of surprised they have not gotten more heat for it - if Facebook ever succumbs its market share to Google I suspect an issue will be made of it. But then, even with search you have to work very hard to make the case that people are "locked into it".