I suppose I didn't make myself clear. Multi-player is not necessarily the only way of "changing your business model" (however, the best solution IMHO). To me, what they need to do is provide services that cannot be "pirated".
For some products, this is support. For others, downloadable content (although it can be argued that this can be pirated as well), general online features (like hosting stats, content, etc).
Stuff like that could seriously improve a customers reason to buy the product instead of pirating it.
How many surrealists does it take to screw in a lightbulb? One to hold the giraffe and one to fill the bathtub with brightly colored power tools.