I also had the same problem with email notifications to customers.
Situation: I created a Quotation, then I Confirmed the sale. When confirming the sale, the customer was being sent an email to follow the document. And that was bad for us.
I deactivated the Customer Portal and now it's alright, customers are not notified anylonger.
For anyone new to Openerp 7.0, the path is: Settings/Configuration/General Settings - Portal Acces - then check or uncheck the "Activate the customer portal" button.
You might give a second look to see whether the customer portal is activated or not.
In my situation, I thought it might be something related to social networking or to followers, but it was a false trace.
Anyway, activating the customer portal has its logic: they are for sure notified when the portal is active.