Looks interesting. Few initial thoughts;

- I'd really like to see a demo or something before signing up (classic "Show HN" feedback)

- Even signing up wont show me how this will work, as I will have to wait for my first email. Right now all I get is an empty calendar

- My calendar appears public. As I haven't received a reminder email yet I don't know what information will be public, but I'd personally like to keep a log like this private (or possibly be able to flag which items should be public)

- Perhaps the calendar data could be exported to Google calendar and/or other calendars people use?