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Intel makes the chipset, not Apple. According to  the chipset supports DDR2 533 or DDR2 667, unfortunately not DDR2 800. Perhaps we'll have to wait until Penryn before we'll see DDR2 800.
 http://download.intel.com/design/mobile/datashts/31627301.pdf Edited 2007-06-05 15:48
i'm sorry, but several sources have stated today, that the new macbook pro is using the intel "santa rosa" platform, which indeed supports DDR2-800.
Did you see the pdf document I linked? If not, check it out. It is the datasheet for the Santa Rosa (i.e. Mobile Intel 965 Express) chipset, in which is states that only DDR2 533 and DDR2 667 are supported. We can hope, however, that the chipset indeed supports higher speed memory than Intel says, but don't bet on it.
If you're going to go by any source today, I suggest believing Intel on this one ;-)