I keep names and addresses of people from whom I purchased a weapon, and if I sell one, I keep a record to whom I sold it to.
Since I have a number of store bought firearms, if anything goes wrong with a firearm I sold, I am the first person the BATF will come to in a trace. While these things can go through many hands, I at least know to whom I sold it to.
I am not a criminal, not intentionally selling to criminals, I know that acting like you have something to hide will only cause Law Enforcement to more closely scrutinize everything about you. I am remember the Blue Card system in Massachusetts, private sales were reported to the Police and the transfer to another individual was recorded on a Blue Card. It did not cut down on crime but it made it easy for the Police to trace guns. If you did not like that, you have the option of leaving Massachusetts, a state I will never be a resident. However, the residents accept this intrusion and it is not an issue for them. Most of what I read in this thread about not keeping records is paranoia based. Recording or not recording sales will not change for one iota the laws of your State. Losing elections changes laws. If the citizens of your state authorize your Government to pick up all guns, you unfortunately, lost the election. At that point, you will have the choice of going to jail, or turning them in. If a gun turns up in a crime and it is traced to you, but you don’t know to whom you sold it, you may have a problem explaining things.