I think it is absolutely true, and it scares the hell out of me!!! I fall right in that gray area where I could quickly and easily go either way. Every bit of me hopes things swing up... but it just takes one bad turn of luck to find yourself low income these days.
I'll tell you one thing, we don't live in a society of single income households anymore. For 5 years my wife and I have attempted it (while the kids were born and being raised) and it has been a constant uphill struggle. We look at families who put their kids in daycare by 3 months old, and while we feel sorry for the lack of bonding between parents and their kids... we are also a little jealous over the financial freedom and "extras" a strong second income can afford.