Play Store star ratings vs. +1s

This is possibly a silly question, but I was wondering how people think about these two features.

In the old days (ie. before deeper Google+ integration came to the Play Store), then star ratings were basically your own personal record of whether an app is good or bad, and the +1 button was a social feature that you could use to recommend apps to friends.

However, now that the Play Store has been integrated with Google+, everything is now "social", including ratings. If you search for any app, you can immediately see what star rating your friends have given it. So what reason, if any, does the +1 button still have for existing?

For my part, I've essentially started using the +1 button as kind-of special sixth star. Like, if an app is useful and does its job properly and works as advertised, then it get five stars. But, if an app is particularly great, to the point that I would recommend it to friends in real life (or rave about how great it is on The Verge), then I give it a +1 too.

However, I've noticed that other people (like Artem Russakovskii from Android Police) use +1 more like a list of public bookmarks of notable apps, including apps to which they assign a poor star rating.

I guess it's a bit like the "favstar" on Twitter - there isn't really any guidance on the "correct" way to use this feature, instead it's up to the users to form a social consensus on what it means?