It's interesting how broad and disjoint the US Federal government is. I'm a Federal contractor and while many of my coworkers are not US citizens, the government does do a quite thorough (non-clearance) investigation on all of us that involves filling out a rather long form, providing past addresses and contacts for each of those addresses, etc. AFAIK they don't do in person interviews for non-clearance background investigations, but they do send out questionnaires by mail to all of the people you list on the form.
