Many companies are "all-in on the web" but aren't in the same position as Google. Look at the recent Chrome profile / Google account auto-login issue. Isn't that an example of Google exercising "control" over how its users interact with the web?
If Google is effectively a monopoly, does it matter if you could theoretically replace all of its offerings? Think about other monopolies in history, I'm sure they had "replacements" too.