As I did with respect to Apple (AAPL), I looked at Facebook’s (FB) capital structure to observe the company’s efficiency in that area. Like AAPL and Google (GOOG), FB is well-known as being a debt resistant company. There is nothing inherently wrong with this approach, as it leaves bankruptcy risk at practically nothing. Nonetheless, debt, up to a point, is a cheaper source of financing than equity given it’s cheap, especially in today’s environment.FB is levered at essentially zero. If one includes non-current liabilities, in general, the company is still comprised of 99% equity. The analysis displayed in this post suggests that FB’s optimal capital structure would be an arrangement approximating 85% equity and 15% debt. For the sake of taking into account market downturns that could lower the company’s market capitalization (equity), it is slightly better to stay to the left side of the peak of the curve (or low point if looking at the WACC v. D/E graph). Being over-leveraged is much more harmful to a company’s value and share price than being under-leveraged.The graph below illustrates the accretive effects of debt up to a point where the cost of capital is minimized. Past this point, the cost of the debt (due to lowered creditworthiness) begins to negatively impact company value/share price. These charts are based on my own analysis of the intrinsic fair value of FB’s stock. I have FB valued at $250 billion, while the market values the company at $291 billion. Accordingly, the values reflected in these graphs will be lower than what would be observed if market values at the time of this writing had been used.Boosting debt up to 15% of the capital structure would boost the company’s value by up to 5.2%.The values displayed do not count the value add from the debt itself.