I absolutely love Joomla, it's a great CMS but can it scale, let's say to the extent of having enormous traffic and users like facebook if I have the right servers and set up my MYSQL database right?
Is there a limit to Joomla itself or does its scalability depend on servers and proper database manipulation?
Let's say I create a membership joomla website that gets very busy and grows big like twitter or facebook , would it be able to scale if I have enough servers?
Probably not. No CMS in common use is easy to scale that far. To do it you'll need to make compromises on functionality or speed and you'll need to get either creative about avoiding database access altogether or creative about wiring your site up to a more scalable data store.
In general it will require an entire team of systems engineers to scale any non-static website to that degree, and using a heavy PHP framework that relies on MySQL by default will likely make that somewhat more difficult.