What does the "allow indexing" tab mean on facebook?

a friend posted the following on her status:
As of today, Facebook will automatically index all your info on Google, which allows everyone to view it. To change this option, go to Settings—> Privacy Settings—> Search—> then UN-CLICK the box that says ‘Allow indexing’. Facebook kept this one quiet. Copy and paste onto your status for all your friends ASAP.
I re posted it (without any research, I always look stupid when I do that, what was I thinking?)
Another friend said it was an urban legend, that she “checked it out,” but didn’t give me any link.
So what does it do when I check or uncheck that box?