I have been reading up on the problems that RICA will have particularly for those people who have no physical address. Here is a thought. It is possible to locate a cellphone number just by using 3 cellphone towers. By figuring out the signal strength to the cellphone is is possible to find an approximate location of that cellphone number. Generally most people sleep at night in their homes unless they are away on business. Based on this, it is possible to figure out where they live based on their proximity to the cellphone tower closest to them.