Wow! You’ve got to look at this chart (click on the heading above to link to the article). Dan Edstrom, of DTC Systems, who performs securitization audits, spent a year putting together a diagram that traces the path of his own mortgage.
Prepare to be shocked, and outraged, and confused. You will be amazed at how convoluted the path is. Boy have we come a long ways from borrowing on a handshake.