An interesting and informative discussion is on at WebmasterWorld. Google's Adam Lasnik was quoted here while he was advising on what type of links can hurt you and those which are safe.
“It's unlikely that your outbound linking is causing your pages to be listed in the supplemental, rather than main index. Also, be assured that we're not looking to penalize folks for a "bad" link here and there. Rather, our algorithms are tuned to look for patterns of "egregious" linking behavior… both on individual sites and in the aggregate.
With that said, it's certainly in your users' interest that you regularly audit outgoing links on your site (especially prominent ones) to ensure that you're not losing folks' trust by sending them to inappropriate places or 404 pages. Sure, it's great to keep Google happy, but it's usually more important (long term) to have your users be return visitors.”