A few questions about Servers

Hi all, not sure if this is the right area to ask these questions.

1. Were the servers that most mmorpg gaming companies use actually designed for games? Or is there only certain types to choose from because of the way the internet is designed? It seems most servers, including the one this forum is on suffer from high congestion and trouble when too many log in at once. Kinda makes me think that servers are like one big room with only one door. Once the room is full, its hard to breathe in it, and you can't all come through the door at once. It seems that with this problem always being a problem, that the hardware engineers would have to completely redesign the way a server works, including a MASSIVE room with many doors.

2. If gaming companies have this problem with overloads, is adding more servers the only solution? And if so, regarding this game, will they be doing that to fix the World Full issues? (haven't heard that they are adding more).