Having one source of income traditionally has been seen as the low-risk approach to managing your career. Work one job, keep your nose to the grindstone and you'll be fine. You won't have a lot, but you'll have enough. Like investing in T-bills, a long-term full-time job meant you were safe and secure.
However, we know that has changed. With more than eight million jobs lost since the recession began, and more than 15 million people out of work, we know that no job is safe and secure anymore. And investing in the debt of other countries is a lot riskier today than it ever has been.