Why even bother? I mean yes, there are a handful of sites which we consider useful and reliable enough to link to them in a very high volume, so high that removing "nofollow" would create a conspicuous spike in the job queue, so high that we've created templates to make them easier to link to. IMDB comes to mind, but somehow I doubt they would be bothered enough to care whether links from Wikipedia affect IMDB's page-rank or whether this would help IMDB pass "Photobucket" in the top 20. But whether they care or not, why should we?
Wikipedia is a very major site, I imagine they would care. I'm not sure why we should though... do we owe them anything for allowing us to link to them? I struggle to see how we would, since they're just putting the information out there, they aren't actively doing anything for us specifically... It would be nice of us to give them a helping hand in their search ratings, but we don't really exist to be nice.