I don't work at Google, so you won't see any proofs out of me (nor of course you'd see any if I did work at Google).
But sooner or later, the browsing habits out of the two active accounts are bound to converge pretty well. Remember you've been tracked not just when you post comments, but on every page out there that has a "+1" button. Then, there will be some close friends who'd be connected on both accounts.
In addition both your real and fake account are very likely to be accessed from the same set of IPs or subnets, locations and time slices.
This may sound complicated, but this sort of mining is just an extension of spam filtering techniques (to which at this point Google invested many millions), and requires zero human intervention. And since it can be done and there is an incentive for Google to do it, it will be done.
btw, I agree that Google will try to correlate account data. That has obvious business value. But it is not obvious at all that Google will flag accounts based on this correlation. That was your statement I was arguing against, not practical possibility of matching various accounts to the same owner.
I could be wrong, but I think Greame is talking about the concept of Pages to create an pseudonym for individuals, not for (small) companies. Apparently you can create a pseudonym on Google+ with Pages, but Pages are mainly marketed towards brands and companies [1], not individuals. It's confusing even for Google employees [2], let alone users.
A support page on YouTube tries to explain the difference between Google+ Profiles, Google+ Pages and Google Accounts [3]. But the fact that a Page can be managed by up to 50 different people suggests, at least to me, that the use of Pages to create and manage your pseudonym is more incidental than intentional.
I did successfully create a page. The problem was that it's still not clear to me how to keep identities separate.
I previously worked for a startup, and had a google apps account. It was impossible to convince Google that the account shouldn't have a Google+ profile, or that it should be the same profile as my personal profile.
And to date I'm still not sure if my page is a youtube account page, a page on my personal account page, or both.
I'm sure there are answers to these questions. I'd say most of my research time was spent making sure that the page wouldn't do something I didn't want it to do, because Google+ burned me repeatedly by unintended behavior.
Google also tends to make things permanent, such as the capitalization of my Youtube account channel. So it's not as simple as "follow the instructions on the page".
If you care about identity, you have to follow the instructions on the page AND make sure the instructions won't lead to something permanently wrong.
That is a good thing when creation of an anonymous account takes some time and/or proof-of-work. That limits spam while providing an opportunity for legit uses of anonymous accounts.
I already had two separate identities. I repeatedly told Google I wanted them kept separate. Google merged them.
There's no clear way for me to undo the damage. Screenshots I've posted for my YouTube configuration preferences don't show what other's equivalent shots do. I'm, frankly, not interested in jumping through hoops to get what Google might offer by way of account segregation now, and change its mind on in another 3, or 6, or 24, or 72 months. Clearly I cannot trust it to respect my specifically indicated wishes, and clearly, the company doesn't respect its users (in many ways, I've detailed these elsewhere including on HN).
Oh, and both identities are pseudonymous. And I studiously avoided circling anyone I knew IRL to avoid outing myself. Never posted photos I'd actually taken, carefully edited screenshots to avoid showing revealing information (though I likely left in a few clues that would help narrow down my identity). Don't mention where I live, where I work, or how I spend my time.
Simply because my preference is to be able to speak freely and discuss things, though really, the "why" shouldn't matter. I simply prefer it this way.
