"Now how many crimes have you unknowingly broke today, citizen"
Well you've just committed one crime, you've shown decent, citizen, by joking about Big Brother ;). So we need to add you to more of our lists. (After all, we need to know who to round up first, when we next want to distract political opponents).
"more data often makes it more difficult to find the needle in the haystack"
The more haystacks they look through the more needles they can find. It'll just cost a lot more to build such a big system. Luckily money isn't such a worry for them. (For them that is, as they don't end up paying for it! ;) ... Ironic really, they use our money to spy on all of us.
As for tangible results, that's a very interesting question. Who exactly is this huge and ever growing distributed system going to data mine? ... I'm sure the idea of it is sold to everyone on the basis its all part of the war on fear, I mean war on terrorists (hiding on every street corner), but that's the point. Is this directed internally as well as externally?
We all know knowledge is power but with a system of such growing knowledge, what safe guards are in place to prevent greedy people in power exploiting this much growing knowledge (and power) for their own gain?
Because each time some more liberty is taken from us all, someone else (i.e. the people in power and their friends with the money) ends up profiting and gaining personally from our loss of yet more liberty.
In which case, Benjamin Franklin, must be spinning in his grave by now, i.e. "Those who would give up Essential Liberty to purchase a little Temporary Safety, deserve neither Liberty nor Safety." ... (Its amazing he said this over 200 years ago, yet still we make the same mistakes).