I lurked for a good while, maybe 2 months or so...
I think the reason that people lurk for so long is because they don't know how good the numbers are, and want to spend the time figureing out if the site is legit or not.
To make people want to join sooner you could make a members only forum. Where they cannot even lurk without joining. This would be the place where PAL charts are posted and such. That would "force" people to join if they were truly interested.
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut