Absolutely they do. There are federal laws that mandate the investigative procedures that they must follow. For example, they must contact any X spouse. Also, the rules have recently changed, I know this because I have a buddy that investigates clearances for DoD. He's actually a contract federal investigator. Apparently, there was a surge and back-log of clearance investigations.

The preliminary investigation is quick if you were NOT granted an interim clearance you would know about it. The company you work for has a security officer. This is a person who has access to a web based system that shows all clearance activity. They are obligated to answer your questions regarding the status of the investigation. Otherwise it is their obligation to inform you, but they slip-up or are busy. Mine happened to inform me about the denial of the interim clearance. Upon further query over the course of many months she revealed to me that the investigation turned up some adverse information about me, "criminal behavior". But the investigation continued. I would did not worry about the past individuals that may/may-not be questioned, but over the years have heard from a few of them that they were contacted, or attempted to be contacted.

Also, if you are denied you have the right to appeal. There will be notification of why you were denied. Your security officer may or may not be active in this process but should be. If you do not have a security officer your boss should be able to assist you in finding out who is. IN some cases small companies rely on partner companies for their Security Officers, because there is some special training that is required.

Finally, when/if an investigator contacts you, be candid, honest, and do not contradict your application. My investigator would ask me two questions simultaneously, it was funny.. I called her out saying, "I'm getting confused because you keep asking two questions, which one do you want me to answer?" her rely, "That's my job." I thought that was funny. They just want you to be candid and honest.

My buddy, the investigator, interacts with his subjects. He'll question them and make them clear up past issues such as delinquent bills, or tickets. We've talked extensively about the process because I was worried about loosing my clearance over filing bankruptcy. Even that doesn't really matter. It's a unique, case by case situation. They are not out to deny people, their job is to verify the facts and uncover anything that was missed. It takes time. It took me over a year. I actually quit that job before the clearance was complete, but federal law states that once an investigation is started it must be finished. So, my old company contacted me and let me know it was adjudicated and Secret was granted.

Seriously, if I can get a clearance, almost anyone can. It's about you, your integrity, honesty and behavior. Past matters, but as long as you own it, prove you can learn from it, and accept the situation you are currently in you'll be fine.

I basically told my investigator that if I wasn't granted a clearance, it would be a loss for my country; that I had no problems telling the world about my past indiscretion(s).

Good luck. Let me know if you have any other questions and I'll do my best.