My personal reaction is that I have no financial dealings with the provider of the SASSIE software and therefore they have no need for my SSN. They are attempting to produce a saleable product by having my personal data and I see no future or benefit to me in that.
There are a number of things you will be asked to do in this business and it always seems to be because "somebody else" is requiring it. You need to make your own, sound decisions about how much invasion you plan to allow in order to pick up a few bucks here and there. One company in their ICA wants you to cover THEIR attorney costs should they be sued pursuant to your work. One company wants you to purchase a criminal background check. One company is saying you just need to undergo a criminal background check to do a bank shop. One company wants you to do drug testing and a criminal background check to go into the store and do audits. Other companies want you to do shops that require a credit check (and your credit score starts dropping like a rock when you have too many 'hits' to it in a year). So what is your privacy or your credit worth to you?