The vital point is that you never know better than your users what content they want. When Nielsen writes that mobile websites should “cut features, to eliminate things that are not core to the mobile use case; [and] cut content, to reduce word count and defer secondary information to secondary pages,” he forgets this fact.
This is a fantastic good read if you have a say (design- or engineering-wise) in how the site looks to mobile and desktop clients. The article goes on to talk about usability studies and possible starting points in addressing the vast mobile audiences.
More importantly, check out the suggested reading by the writer, “Mobile-friendly: The mobile web optimization guide”.