Besides the obvious 3 or 4 years and 5 or 6 hundred million dollars they've poured into it, and the hardware, you can set up something that is similar, though quite a bit smaller using either of the versions of Links.
The best thing to do is look in the resource area, and see what other people have done with Links.
For what is required, you can check the home page here, or for Link SQL check the FAQ for some peoples experiences.
------------------
POSTCARDS.COM -- Everything Postcards on the Internet
www.postcards.com LinkSQL FAQ: www.postcards.com/FAQ/LinkSQL/