I think a mine layer would work better because 1) you wouldn't have to build two starbases first 2) You could place them anywhere like in a ship hot spot or a freighter line.

Mmm... minefields...
I liked Rasori's idea.

I dunno about you, Shadow, but I'll trade with the Drengin even if I'm good. They're my enemy, but it's my trade route. So, how do these mines determine who's friend and who's foe here?

Yes, like that. Like if you have your ships auto-attack when your not at war, they wont shoot or move, same thing.

Yes, it would be huge! making it even more cool!  

if a ship had a sensor range of 5,000,000 miles (space is big), a mine would probably have a similar sensor range too, so it may be huge, but you wont need that many mines.

While you are correct in that any wall of mines would have to be laid in a plane, or a spherical shell to cover a planet, there are a few points to consider:

-You have to know the minefield is there to avoid it.

-If you know where the target is going, you don't need to mine quite so large an area.

-We can assume space mines won't be direct contact mines. Those would indeed need absurdly high density to hit anything. Instead, they would be more like missile launcher-armed buoys that launch at anything that comes in range. This would allow each mine to cover a decent area.

-While space is 3d, star systems tend to be rather flat. Everything of any importance is located within a few degrees of the ecliptic. That may not matter much in interstellar space, but inside the system it's a significant factor.

-This is not a reality simulator, it's a game. Specifically, it's a game that treats space two dimentionally. Thus a ring of mines would be effective around a planet, even though you might need a sphere in reality     

My personal plan of attack: a high speed minelayer with one point of any weapon. Dash in, blow up asteroid mines, mine asteroids to kill off miners trying to rebuild. Also effective to mine around an enemy starbase, to kill off constructors trying to upgrade it   

I like your style, blow 'em up if they change their lousy contract.

But actually, why are the miners so vulnerable to another cultures imfluence? I mean you could provide for the things for 10 years and they would still default. MAybe you could have asteroid loyalty, or give them raises to shut them up.

And you're good?

Well if you were evil you could just put a fail-safe system. They would cheer and jeer.....little did they know they had cyanide pills put in their brains and they are now leaking into their brains!

One possible justification for space mines, outside of the automated, one shot missile launcher idea (or perhaps as an extension of it) is that the warheads could contain some absolutely absurd yields. After all, movement capabilities and space aren't much of a concern on what is essentially an auto tracking disposable missile tube. If you have the capability of sending high yield nuclear devices at a target, a single mine could cover a very wide space while retaining a low profile and cost. Hell, a society advanced enough to manufacture antimatter in large quantities (admittedly, that's pretty advanced) could stuff a couple kilograms of the stuff in and make one HELL of a big bang.

The only catch is accurately detonating the damn things when your target is a light minute away.

A homing device wouldn't help matters, since it too would be bounded by the time lag and accuracy issues.

Probably, the best way to go about it would be miniature warp drives on the mines themselves, and just launch themselves at the target. They'd be expensive as all get out, but that resolves the accuracy issue.