After a home buyer secures a loan from a bank (i.e., a mortgage), the bank often securitizes the loans, which means they package them for sale to investors. This process is much easier if the loans are backed by Fannie and Freddie, the government sponsored mortgage agencies. Fannie and Freddie, however, will only back loans below certain values -- the so-called jumbo loans. This amount has generally been capped at $417,000 (although higher in certain high-cost areas). Regulators plan to lower these caps, which means jumbo loans may be harder to come by since it will be more difficult to securitize such loans. See article here, LA Times.
Dolvin, Steven D., "Jumbo Mortgages and Securitization" (2013). All Chapters. 80.