I don't like the CMCs much; they are mining my strategic mineral reserve. I might not need it now but in 2-3 years I certainly will, the income is neither here nor there, the lost minerals are since geology teams are restricted to 100,000 tons now, and if I pay 250 per complex I will spend more time just boosting the domestic economy 
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To place ten automated mines (which is the same output as 1 CMC) would cost 2400 wealth and use 2400 tons of minerals and use up industrial capacity, plus with a CMC you get free mass drivers, a free sensor and a free Garrison unit so they are good value for money if they are on a system body you want to mine. Don't forget you can add your own mines and other installations to the same colony as well. If they set up on a system body you don't want, then ignore them and take the money.
In my current game, there are seventeen civilian mining complexes in Sol spread among five colonies. I am leaving a couple of smaller colonies to go to civilian sources (and receiving the tax income) as I would never establish mines on those bodies anyway and I am receiving minerals from the rest (13 CMC), which is costing about four percent of my total expenditure. Setting up and moving 130 automated mines, plus mass drivers, etc, would have cost me a lot of money and minerals. I am saving the automated mines I do have for system bodies in those systems where CMCs woud never be established (i.e. no colony with 10m+ pop).
Another option is to find a system where there are a lot of mineral sources that would allow CMCs but that you probably wouldn't bother with, such as system bodies with Duranium at 0.7 or higher but no other minerals or everything else at 0.1. If you establish a 10m+ colony that will allow the civilians to setup CMCs in the system to generate extra tax income.
However, if there is a system body you want to mine and you really don't want any CMCs to set up on it then just put a empty colony on it and they will ignore it.
Steve
