Yes, maybe for new site. But what to do if site was PR5 and now it's PR0. In that situation link building doesn't help much.
Surely... if it is a well trafficked site. Anyway... there is no harm in getting a link from such sites as they would come very cheap and might give you a PR juice as and when that site sees a good elevation in its own rank in future! Regards, RightMan
PR0 means your PR juice is low, or saying not able to achieve the PR1 requirement To get better PR, you need to build link which to gain PR juice