It's all subjective really. DRM in my opinion is a way of basically saying, "We don't trust our own customers so we are going to make it harder for you to use your legitimate purchase on multiple devices, multiple times." the proof that DRM doesn't work? Look on The Pirate Bay, count the number of video games alone protected by DRM that have been cracked; Diablo 3, Starcraft 2, Battlefield 3, Modern Warfare 3 and so on.
The money spent on DRM is a waste, no matter how smart you think your DRM implementation is, there are people out there smarter with tonnes of free time to crack your DRM. Want to know what the best DRM implementation is? No DRM. Why? you won't make your customers feel like criminals which in term will make them not spite you. See how angry people get at those, "You wouldn't steal a car" anti-piracy adverts at the beginning of their purchased and rented DVD's? Perfect example of treating your customers like criminals.
The bottom line is: if people want to steal your stuff, they will eventually find a way. Is it worth the extra added effort and cash to implement something you know for certain will be cracked? I don't think so.
Just my two cents.