If you have read the news lately, you will know that Wikipedia has decided to put the nofollow tag in their outgoing links. The nofollow is a tag that tells the search engines that the external link is not vouched/recommended by the website. It was meant to combat comment spamming. The linking between websites is the basis of PageRank, the algorithm behind Google success.
Wikipedia has earned its success, popularity and authority with the amount of incoming link love that it receives every day. It is quite odd and hypocrit that Wikipedia decides not to give back the link love.Search for any celebrity on any search engine and you will see Wikipedia on the top spots (often number one). This is because of the amount of incoming links. If the amount of incoming link were invalidated, Wikipedia would fall in the anonymity and be several pages down the SERPs (search engine results pages).
From now on, my link to Wikipedia (if any) will be with the nofollow tag.