RegDCP - 4:51 am on Sep 18, 2012 (gmt 0)
They are their rules.
TOS. Terms Of Service.
The obligation is you follow their rules or you get turfed.
And while they phrase them as guidelines in some cases, the TOS clearly states:
Welcome to Google!
Thanks for using our products and services (“Services”). The Services are provided by Google Inc. (“Google”), located at 1600 Amphitheatre Parkway, Mountain View, CA 94043, United States.
By using our Services, you are agreeing to these terms. Please read them carefully.
Additional terms will be available with the relevant Services, and those additional terms become part of your agreement with us if you use those Services.
Using our Services
You must follow any policies made available to you within the Services.
Looks pretty clear to me.