They already do that, in Google Notebook, and it frustrates me a little. Every time I want to add something to a public notebook (which is really a poor man's blog — or at least I use it that way:), I must make one additional click to "Yes, I understand this is public. Add it, damn!". And the Notebook even has a nice color coding of private (blue) vs. public (yellow) already. At first I thought it was because of copyright concerns, but then they bought YouTube. ;-D

My advice is add a check box for public or private instead of notice. Save the user's time.
So you can define per line event for public or not.

You can define per event if it is public or private. That said, why anyone would store any kind of public information in a private calendar is beyond me.D

> They already do that, in Google Notebook, and it
> frustrates me a little.

Maybe as a compromise they could have a little checkbox "[X] Ask me again next time" or something...

username: chris.b
password: aligator3

crap... was that private?

chis...

Technical details of permanent failure:
UNKNOWN_USER: No such user