They are nofollow links (so no effect on PR). However, if they are relevent to the discussion, they can generate good traffic.
It's safe to assume that even though the PR juice may be ignored, the surrounding text will also help your rankings. If the answer is a long one with lots of good text, the link should help.
no its not safe to assume so. nofollow links are completely ignored like they aren't there. otherwise there would be no point in inventing the tag.
thats correct. nofollow links are useless. to check for them just highlight a link on a page and click view selection source. If you find that there is a rel= "nofollow" tag on outbound links then you are wasting your time unless ur sending visitors to a genious site they'll like and return to.
Sometimes I wonder though. The nofollow tag could easily be a way for Google to test sites. In a weird way...the nofollow tag might actually make a link worth more. Just a theory mind you but I would love to test it.