I fail to see why this is a "deeply symbolic moment in the history of operating systems" and not merely a moderately interesting moment in the corporate history of the respective companies (or, more specifically, in Red Hat's corporate history). Red Hat may represent Linux, but it's not Linux, and market capitalization, being a function of share price, is a less interesting metric then any measurement of the actual use of the operating systems these companies produce. Anyone who remembers the Red Hat IPO will know that share price is more closely tied to hype than to particularly signficant tecnical advances.