Triple channel DDR3 and new Intel processors

As far as I know, DDR3 memory is supposed to be installed in triples (for instance, 3x2GB=6GB) to achieve triple channel performance, just as DDR2 was installed in pairs (2x2GB=GB etc.). Am I correct?

New intel processors have a memory controller in the CPU. It says on Intel's product pages that most of those processors support "dual channel" but require DDR3-memory. Isn't this odd? Won't it cut down the performance, supporting only dual channel (the most expensive Core i7s support triple channel)?

 

Core i7-900 series supports triple channel DDR3. Core i5 & Core i7-800 series support dual channel DDR3. The memory speed of the dual channel is 1333 MHz instead of 1066 MHz on the triple channel. These are the "officially supported" speeds, going by what I have been reading. Also, info that I have points to better overclocking performance with the dual channel. Have not tried it first hand tho. Anyone have any numbers they can post ?