28 Jun 09
23 Mar 11 8:51 pm
I don't think it would hurt your rankings for very long, unless you were already ranking well for whatever terms were on the page that you are trying to rank for. I think you might notice some downward movement for a while. Now, if you were going to this on a page that had been up a year or two and had really good rankings on a competitive term, then that could affect your rankings. But if you're just getting started, I think the dip would be so negligible you would hardly notice.
My brother might be able to provide a little more insight into this, because I know he's made several sitewide changes over the last year or so as he tried out different things. But that would be my guess.