Reader Bob Thornton professes to be a simple user with a simple question, and that question is:
In Numbers, when you create a formula how do protect that cell so that someone can not accidently erase the formula?
The simple answer is: You can't, at least not in the way you can protect Excel cells. A small consolation is that you can lock tables. So, you could create a table for your numeric masterpiece, select the table, and then choose Arrange -> Lock. Your work would be safe until someone chooses to unlock the table.
Another technique recommended in Apple's Discussion Forums is to do your work and then plant a rectangle over the area you don't want changed, select that rectangle, open the Inspector, click the Graphic tab, move the Opacity slider all the way to the left (0%), and choose Arrange -> Lock to lock the shape in place. The work beneath the shape will shine through but no one will be able to muck with it unless they unlock the shape and either move it or send it into the background.