Processors with unlocked multiplier are mainly targeted at enthusiasts. The thing is, Sandy Bridge processors can’t be bus clocked. Motherboard south bridge has an integrated clock generator with its BCLK locked at 100MHz.
CPU overclocking is now possible only by multiplier adjustment. K-indexed models support multiplier change up-to х57. However, the price for these model will be significantly higher compared to basic models. Still, there are some ways for CPU overclocking in non K-indexed models — unlocked multiplier in Turbo mode. Processors with lower TDP level won’t have a chance to be overclocked. I am not sure if this will please all the overclocking fans.