It's true that anything you sync with the Google calendar (if it has a contact attached) sends out an invite to the contact (even from past events). This is a devasting flaw and a game stopper for many of us.
Other systems are having the same problem, but their work around is not bad.
All they are doing is instead of mapping the contact to the google contact fields...they are mapping the contacts to the notes section field. That way you can still see who the meeting is with and that way no invitations are automaticaly sent!!!
Any chance of doing the same until Google resolves this issue (which may be never)?