Do you think that linking to a site that's been banned from Adsense could have an impact, one way or the other, on your site or Adsense account?
Do you think it's possible that when they ban a site from Adsense they take a look at some of the sights that are linking to the site they just banned? Good point though...99 out of 100 times it would be impossible for someone to tell if a site they were linking to was banned from Adsense. I had just noticed one this morning and the question popped into my head.
Anything is possible... either way, I wouldn't spend more than about 1 second thinking or worrying about it though.