Matt Cutts: The reason I would use NOFOLLOW is if you truly don’t want a page indexed at all.
Take a log-in page for example, Googlebot doesn’t know how to log in and that’s not of any value for users to have. I can imagine that a disclaimer or a privacy statement could be kind of useful.
So you can put those links on. It’s not like it’s going to cause you a spam penalty, but truthfully I would tend to worry more about having enough good links because you have enough great content that you tend to get a lot of people linking to you and you tend to get a lot of good coverage in Google’s Index.
It’s a second order effect at best. I really wouldn’t spend a lot of time saying, “I’m going to NOFOLLOW all my links to my stuff that I don’t care about.” Typically you’d do better by maybe linking or not linking to stuff.
Don’t worry so much about sculpting. That tends to take a lot more time and not really be as big a bang for your buck compared to just putting your efforts in on making great content that will attract links.