see previous comment here http://news.ycombinator.com/item?id=3298594
Keep in mind that there are probably north of 1 in 150 Americans with current access to classified material. It's a huge number and just because you aren't in the club doesn't mean it's really all that hard to get in. Get a job that gets you a clearance and you can see what's on the other side of the curtain. Believe it or not, it's amazingly mundane.
At TS it starts to get more restricted. You have more ability to request access to things outside your general area, but you may/may not get approved.
In the Compartments, my experience has been they are surprisingly global in nature, but focused in content. Meaning I can pretty much get that "kind" of information for any place on the planet, but it's only that "kind" of information. There's some exceptions, but not many.
SAP programs tend to be where it gets very focused. Often because they represent information only collected in your area using only a specific means. So there isn't a global collection of that kind of data -- well, there might be, but you aren't in all of the SAP programs to try and figure it out.
Also, once at the TS/SCI level and above everything in compartmentalized. It isn't as if you get the clearance, get some password to some digital book of secrets and all of a sudden you know what really went down at Area 51.
Also, I work with plenty of people with TS/SCIs who have used drugs in the past.
The key is just being honest with the investigators.
You are right that people with too much debt, gambling problems, current drug use, etc. don't get one. But that makes sense. I've worked with some pretty sketchy characters though and they didn't have a problem getting or keeping there clearances.
I don't think I've ever personally known somebody who had theirs denied, I've known one person who had their taken from them for doing some questionable things.
Quite often it could be that the investigator could not ascertain the relationships on the wife's side and/or they don't have a citizenship yet.
I've worked on SAP programs that had 3 people on them. Some of the larger compartments probably have hundreds of thousands read into them.
http://www.slate.com/articles/business/the_dismal_science/20...
I bet this sort of thing happens all the time.