My wife finds that her iPhone constantly reminds her of google calendar events (accessed via the exchange trick). None of the google events have reminders enabled. The phone preferences don't ask for reminders. Yet reminders she gets.
By default Google calendar is configured to send notifications for events. Go to http://calendar.google.com/. Select the Calendar Details -> Notifications. There is an option 'By default, remind me via...'. Click on the remove link to get rid of the default notification.