This is not a "private information leak." It's expected behaviour. Entering information in that field to create a new event results in Google Calendar parsing your information as best as it can, to automatically set things like the date, time, event description and of course, the participants (the apparent privacy leak here.)
Why then, does a notification dialogue box pop up when you enter the information on the calendar overview page?
Evidently, someone thought it was a good idea to warn there that an invite was going to be sent. So why does no warning pop up when you're in the "Edit Event" view?
If you're aware of the feature, it's not a privacy leak. If you aren't, it could be very damaging.
It would have been nice if the first time the Calendar parsed and sent emails on behalf of a user, it would ask if this is what they wanted. It doesn't have to bug them ever again, but that's a single instance of training that would minimize confusion.
Personally I kinda wish we could use different terminology for this. When the phrase "leak private information" is used, I think of Target losing my credit card info. In this case a more accurate title would be "Google Calendar Sometimes Sends Emails on Your Behalf which You May Or May Not Want." Granted this title sucks and is no where near any kind of quality link bait.
