It is interesting to see how the rel=”nofollow” attribute has been used and by whom since it was introduced.

Wordpress has the nofollow attribute as default on installation. (sidenote: Should you not reward those who put the time into commenting on your blog?)
Wikipedia has nofollow attributes on external links.
Many forums also have nofollow attributes set for signature links.
All of this to mainly combat spammers of course.

As far as I know Yahoo will still follow and even put the page in its index, even if it has this attribute.

Spammers aside, the no follow should keep more PR on that particular page. (if you care about such things).

I am wondering if using a noindex, nofollow attribute combination on pages such as logins etc. would be the way to go. The noindex seems to be a bit better supported, although last time I checked Yahoo was again the odd ball out.

Now what about this, you have links in your sidebar, and those links again in your footer. Would putting nofollow attributes in your footer links cause any problems?