Nothing! Lots of people do that, I believe.

The problem is this bug would have let me easily find out your secret YouTube email address.

You then have to be very disciplined about logging your google accounts in and out, and either give up on tabbed browsing or have a youtube-only browser and an "other" browser.

On Android, you don't have this choice.

I deleted my whole Google+ profile in order to disconnect the connection I accidentally made earlier. It was the only way I could see to do it.