Good thing Google didn't do that. The blog author says right up front he agreed to the new terms.

And they didn't sign him up for anything, they upgraded his account. Still a single account, still with a single company, still with the same cost, still with the same privacy policy, still with the same everything - except it does more, now, if he so chooses to use the extra features.

Let's not pretend that Google are acting out of altruism. The blog author says that he was agreeing term for Picasa, not G+. It doesn't matter that the service is "free", the expansive privacy policy may be the same, it just covers more of the users online activity without their direct consent.

So, if you're running a... time management tool, let's say it's just a todo list. Then you create another tool, a time tracker so you can log your hours on your todo items. You should force them to sign up for it in order to use it? Personally, even if the tools were made to be able to operate separately of each other, I would give the users of my first tool access to the second one and link the accounts.

G+ is just an extension of their offerings. Just because the tides of the internets have flowed against it doesn't mean that anything involving Google plus is practically rape.