Originally Posted by n-ster
What exactly do theses DRMs do? Do they do anything negative to the legit buyer?
They, by definition, influence the legit buyer. These programs consume system resources (albeit a small amount), force connectivity to the parent company, and have a track record of borking systems should the wind be blowing in the wrong direction.
If you'd like a brief history, search these forums for Punk Buster.
Steam, in my opinion, was the first group to get it right. Minimal intrusion, friendly interface, and convenient structure. Before attaining this, Steam suffered through its early crappy phase.