Google Play just updated my Garmin Connect Mobile app, and I was startled (and dismayed) to discover the new version displayed my birthdate in my profile.
I immediately set my profile privacy go "only me".
Previously only my age was displayed, and that's how I wanted it.
Knowing your date of birth makes it a lot easier for someone to steal your identity, and having mine stolen again is not something I'm willing to risk. Once is one time too many.