Holy shit! Why would someone do that.
And NO, I am NOT happy about that!
It's because someone associated with DP (take a guess) was spamming DP links in various articles, as well as vandalizing other pages (removing links to AtariAge and AtariProtos.com, for instance). They left behind a pretty big trail of evidence, and DP was subsequently blacklisted from Wikipedia.
..Al
There was no "they." DP.com is currently blacklisted, whatever that entails. The Wikipedia entry for DP was removed on the basis of notability, and there are still a bunch of articles that cite the DP website.
Edit - edited info on blacklisting