I sometimes wonder if Bitcointalk.org will be able to sustain the amount of constant influx of new users and tons of posts daily. Will the site ever become an invite only sort of thing? (you need an invitation of someone to register). This has happened with most forums that reach an insanely big amount of traffic. If Bitcoin goes mainstream I can see how could this happen.
They cant do that. Bitcointalk will cater as much as bitcoin users as possible. Its their job to upgrade the site to cater the influx.
The reason it will be able to handle the influx of people is because more users on the site mean high ad revenue, and more ad revenue means more money to pay for servers and bandwidth to handle more users.
I would also highly doubt that bitcointalk would ever go to a "invite only" model. They may halt new account registrations if accounts are getting registered too quickly (as they have done before)
That is correct the site is not only here to educate us but also to make money. I dont know how much they get from ads, but I know its a lot.