DRM often gets a very bad rap because it's usually very bad. But you have to hand it to Croteam for the 'DRM' on Serious Sam 3; it's a giant, immortal, annoying red scorpion.
The DSOGaming site reports that, " if you are one of those greedy gamers that wanted to play illegaly this polished FPS game, beware; an immortal speedy red scorpion/arachnoid will come after you until you drop dead."