I often mention the problems associated with multiplayer on a large map, I thought I would explain in more detail what the primary issue actually is in a way that everyone should be able to understand. There are many issues with what SFB players call an "open map", but these are the two really big ones that must be addressed in some way to avoid... an unpleasant experience for the player.
Imagine yourself playing me, here are the two worst things I can do too you on an open map...
The first is simple. With unlimited room to run and a significantly faster ship I can "grief" you forever by just staying out of your range. As loooooooong as I want too. There is nothing at all you can do about it, except quit that match and not play with me anymore because I am a jerk "Speed is life", it's an immutable law. A truism, an axiom.
The next thing is a little more complicated to explain, but is basically me using the same principle from the first example in a far more annoying way. In SFB terminology I can use the Oblique Attack to repeatedly achieve the Oblique Option Point. We have a specific name for this tactic, it is called "The Klingon Sabre Dance". In layman's terms, it means that I can approach at an angle from outside of effective weapon range already half-way through the turn away ("The Oblique Attack"), firing at the edge of effective weapon range ("The Oblique Option Point") and turning away to either circle around, fly a figure-8 pattern, or simply turn out and back in in a wave-like pattern. There is nothing at all you can do about this, assuming I am in a significantly faster ship. Oh, and the Sabre Dance is lethally effective in Star Control, where your health does not regenerate.
Now, imagine yourself as my opponent in a 1v1 duel. Are you having fun? I certainly am, but I doubt you are. I bet you'd appreciate a smaller area that interfered with my ability to do this too you, wouldn't you?
These are the two really big issues with an open map, there are others, but these are the potentially game breaking ones that need to be addressed in some way to prevent winding up with what is an ultimately boring combat environment. The "best" solution the SFB community ever came up with to address this issue is a "Tournament Map" that was just the right size to allow the faster ship to control the range, but small enough to limit and contain the retrograde (the Sabre Dance is an extension of the concept of the retrograde).