I too got this mail from google.
It says i have to register my existing API-key-account to a 'billing-account' with monthly free costs of $200.
Otherwise my key won´t work after 11th of June.
This is a major change and i am not sure, if the traffic (map calls of my customer projects) will exceed this $200 or not.
So i am wondering, nobody else - only 'clio' reported this here...
This should effect all googlemap plugin users!
Do we have to swap (again for me) to bingmap to avoid monthly costs?