Barefeats.com tested a unibody MacBook Pro back in December to see if it would accept more that 4GB of RAM. They found that 6GB worked (4GB + 2GB), but 8GB caused system instability. The same configuration also worked in the unibody MacBook. Since the mini is based on the same architecture I assume that same thing applies to it too. Unless they built it off the 17" MBP, which can use 8GB.