Mike...
Maybe create a form for folks to use instead of allowing write access to the spreadsheet.
Yep, in hindsight, that would have been the way to go. That was my first time creating a public doc for everybody to edit, so I went with what I was familiar with. On the plus side, some people made great contributions, like the charts, the conditional formatting, etc. I'm reluctant to make it a form now, there are over 170 rows and I doubt people will fill out another form again.