In the Swan orientation video, Dr.Chang warned that attempting to use the computer to contact the outside world could lead to another incident. But we know that The Incident had nothing to do with communication. So why would Chang emphasize this supposed danger of communication? Simple. That's not Dr. Chang in the Swan video. That's MIB impersonating Chang. Think about it. MIB is the one who is dedicated to keeping the island hidden. And contacting the outside world exposes the location of the island. Hence Chang's emphasis on not contacting the outside world.
This leads into my much broader theory about the true purpose of the Swan. As some fans have already realized, there seems to be a correlation between the two energy pockets on the island and the two competing entities, Jacob and MIB. Jacob's goal is to bring people to the island. This links Jacob to the Swan's energy which was responsible for bringing 815 to the island. MIB's objective is to keep people away from the island. This links MIB to the Orchid's energy because that energy has the ability to move the island so it can't be found.
My theory is that MIB is responsible for the construction of the Swan station because it was a way to impair Jacob. The Swan contains the energy while keeping it controlled to prevent build up. The Swan is the reason MIB was able to plan and execute his elaborate scheme of instilling Ben as leader of the Others, making Locke appear to be a savior, impersonating Jacob in the cabin, etc. MIB was able to do all of this because the Swan was containing Jacob's energy leaving him severely impaired if not completely powerless on the island. And since Jacob could not stop MIB on the island, Jacob had to arrange a counter move off the island, hence the touching of the selective Losties. I won't even bother speculating what Jacob's plan is exactly or the meaning of "They're coming." I think all the possible interpretations of Jacob's dying words have already been covered many times on the this site alone. We just don't have enough information to be sure. But I believe we've le! arned enough details about MIB's plan to construct a fairly accurate image of his grand scheme.