It could be discussed in the abstract but it's difficult to separate. I considered posting this in the pensions forum. Pensions are the practical application for most people.
I think yoganmahew's point about the limited availability of funds does deserve a discussion of its own, it's certainly something that frustrates me. The present limited range of funds to select from in pension schemes makes it difficult (impossible?) to pursue alternative strategies. How willing and able are pensions providers, brokers, trustees and regulators to give the consumer products that would give them more information and control. It's possible to do this outside pension schemes so why is it so difficult within them?