Considering personal net worth is a function of income and expenses, I'd have to agree with Uncephalized in terms of the technical definition of net worth, which is total assets - total debt.
If you have positive net worth, your income and expenses are the moving part that helps it jump up and down, potentially into the negatives. If your assets suddenly decline in level to a point that it is outshadowed by debt, it's your own fault for investing in that certain asset in the short term. Although liquidity is king right now, if you know how to time things correctly and manage your ffinances, your net worth shouldn't fluctuate to the red during a financial crisis. But this is assuming you had a good chunk of assets to work with to begin with.