Yesterday we told you that Google tops the list of heavyweight stocks in terms of “market capitalization per employee.” There’s $8.6 million in stock-market value riding on every Googler who works for the company.

It’s an odd metric, yes. The post generated some amusing comments. David Emery in Reston, Virginia wrote, “This seems to be a good justification for Google’s well-known investment in/pampering of their employees. Happy employees generate value-per-employee, I suspect.”

Another reader noted that Gilead beats Google on this particular metric. The biotech company, with $40 billion stock-market value and 3,400 employees, boasts an impressive market cap/employee of $11.7 million. The power of pharmaceuticals.

So, what are the biggest U.S. companies by market capitalization?

It’s fascinating to see that Apple — which, due to strong earnings and new-product excitement this week, rose to the top five — stands a chance to eclipse Wal-Mart in stock-market heft. Apple, though, is still a long way from touching mighty Exxon Mobil .

The 10 largest U.S. companies by stock-market capitalization are:

1. Exxon Mobil: $353.23 billion

2. Microsoft: $249.9 billion

3. Wal-Mart: $194.3 billion

4. Apple: $183.88 billion

5. JP Morgan Chase : $179.84 billion

6. Google: $175.93 billion

7. Procter & Gamble : $167.3 billion

8. Johnson & Johnson : $166.2 billion

9. General Electric : $161.42 billion

10. IBM : $159.08 billion

P.S. Besides Gilead, do you know any companies that beat Google’s stock-market value per employee: $8.6 million?