Hi James - I am indeed one with ambitions of having millions of registered users eventually.
I have extensively modded my site to create something I believe will be very attractive.
I even integtrated PostAffiliatePro which is a fully featured affiliate software so that I can reward my members- and I am also integrating a full shopping mall so that all members can sell their own items through paypal.

I was hoping your post would cover some of the difficulties to be expected when dealing with see more large numbers of members. One of the selling points of Dolphin 6.1 was its 'scaleability'.
Would you be so good as to comment on how many members Dolphin can generally handle, and what sort of upgrades of server (or other factors) it would need when reaching certain sizes?

I have read that Dolphin is very slow because of the way it accesses some info in the database.
In particular I read that the friends feature needs overhauling if people have thousands of friends.
Care to comment on this and other factors?

Thanks for your great contributions at your site, they have helped a lot!
Dan V