OK, I think I'm getting the picture. Part of my problem is just the new terminology.
Is this right then....
One GPU runs one miner (one instance of mining software).
One "Mining Rig" with 3x 6990 cards would be running six miners.
10 mining rigs heating up my basement would be running 60 miners total.
Since there all under my control this would essentially be my own private pool.
All of the miners would do the "getwork" protocol business with my own bitcoin server that would dole out the work
and the bitcoin server keep track of the blocks that the miners all work on.
So somehow my bitcoin server divides out the work, and all my 60 miners are solving the same block.
But in the bigger, worldwide picture, does that mean that all miners in the entire world are working on the same block?
That would seem to be true if the blocks must be solved and chained in sequence.
Then the whole worldwide mining process would devolve into a giant hardware/software "arms race" where whomever has biggest and fastest pool of miners can collect all the coins. For example an evil consortium could assemble a pool of 2^32 miners and be done really really fast
Sound like little guy solo miners have a pretty slim chance at this.