I think the issue must still be in how exactly they define "sell-in", because for whatever reason a certain percentage of the units they are selling-in don't seem to sell-through
Yeah I've often wondered about this...a lot of units probably "fall through the cracks". Lets say one example I can think of, Wal Mart display kiosk units. Theres probably a lot of those, and further they probably break and need replacing a LOT. You add this up across all retail stores and it could become a significant, if minor, number of units, that is counted as "sold in", but does not go to any consumer sell through. What about promotional units, ones given away in contests and such?
There are probably a small but significant percent of consoles that are "sold in" that never end up in consumer hands.
I do think PS3 fans have a legit gripe, for once, about the sell through versus shipped discrepancy on this site. Unless Sony is playing loose with their shipped figures somehow. If anything, I would think the Sony sell through would be greater than the other guys right now due to their shortage issues.