Today specifically, google has changed everything.
ALL your settings for all google services in existence are now all tied to a single user account. You don;t need to be logged in to use most of the services (Search, maps, etc), but their behaviour won;t be the same and to get full features you have to now be logged in...
It's quite thing they've done. Europe is not too happy about it at all, nor are quite a few higher ups in the U.S. It's quite a leap into the future world where every single thing you do every second of the day is recorded and made public for everyone else to see (assuming they have money to pay google to see it).
They are touting things like if you search for "lemon scented candles" on goggle that you may now be emailed "Fruit scented candles" spam (and to your G+ account etc) because they are all now completely tied together... Horray!