Q:

Droid - what won't function properly on device if I disable background data usage for google play store?

I just upgraded to a new droid razor maxx from an older version.  With the older version I never went over my 150 mb of data.  Since I received the new phone Google Play Store is eating up my data and I went over my limit within 3 days. 
Why does google play eat up all my data using mostly "background" usage, when I am not even accessing it?   
What won't function properly on device if I disable background data usage for google play store?

A:

I have done that months ago for the very same reason, so I can tell from my own experience:

you will no longer receive update notifications while on mobile data (naturally)
no apps will auto-update while on mobile data (again, naturally)

Both is what you want. I encountered no more restrictions. Update notifications coming in as soon as the device is connected to any WiFi, updates I either do on WiFi only.
What I didn't try is to force an update/install while on mobile data. In theory, this should work as long as you keep the app in foreground – but the installation will stall as soon as you switch to another app (as then Google Play no longer is the "foreground app"). But that's the theory only, as I've never tested it.

