So, why add salt to the water in the first place? Salt should be added to the water because every element of a dish should be seasoned. The salt adds a slight saltiness to the pasta that enhances the flavor considerably. Cooking pasta in salted water means that the pasta will absorb some of the salt and therefore not taste bland. This can't be fixed later by salting the pasta after it is cooked or adding extra salt to the sauce; this would just result in a bland pasta with a salty exterior.
So, how much salt should be added to the water? As a general rule of thumb, and what I have also heard from Mario Batali; is that the pasta water should taste like the sea. I even go as far as to season my pasta water with sea salt, another tip from Mario. I hope this didn't come off as being too preachy; I just wanted to get that off my chest and stress the importance of properly seasoned food. The dishes I had would have been saved by simply adding some salt to the pasta water. Thanks for reading.