I am a bit surprised by some things in this article... for example:

"Generally, the rule of thumb is to have as much as RAM as your data file is."

Is it really so? Isn't there some limit from where this rule does not apply? Our data file has over 200 GB, but I have never seen a server with that much memory. Obviously, it would be terribly expensive... I don't think databases around this size are rare, so what is your opinion about their memory requirements? We are running this DB on a box with 8GB RAM; I suppose it would work better with more memory, but the performance (with 20-40 concurrent users) is quite good.