Again with the anonymity. The likes are pseudonymous, and currently, tied to your Google account (but not necessarily g+). So should people be allowed to have more than one Google account?

Is spamming likes really a problem now, and will the SEO target evaporate once the number of accounts is reduced? I don't think so. Quite the opposite, actually.

You say people should not have to see ads they don't want to see - good luck with that. A good deal of marketing is selling to people who aren't looking to buy.