Activity 5- Google Docs

Opened a spreadsheet,created contacts list,shared file, created graphs and had all contacts update the spreadsheet at once watching live graphing which was Ok until someone started sabotaging and we could nolt work out who. This got us to thinking how would it be if 30 studetns were in the classroom working on the file at once, could present a problem. i am sure their will be ways to incorporate with a little more experience. Setting up the contacts list could be time consuming as all will have to have a gmail account.Hoping there may be an easier way to update 150 studetns into contacts list.