A desire to participate in corporate strategy decisions at the highest level led Mark Okerstrom first into corporate law, at London firm Freshfields; then to investment banking at UBS; then to Bain Consulting; and then to his current role as CFO and executive vice president of Expedia. The $3.5 billion online travel company was once a unit of media mogul Barry Diller's IAC/InterActiveCorp, and Diller still holds sway as its chairman.

Since arriving at Expedia in 2006, Okerstrom, 39, has presided over more than 20 transactions, including last year's divestiture of travel review and advice site TripAdvisor, as well as Expedia's most recent acquisition, in December, of a $632 million majority stake in trivago, a German online travel company. Expedia is striving to expand its reach internationally and build its market share in travel bookings from a current 3% of the $1 trillion industry.

When Okerstrom joined Expedia in 2006 as a senior director on the corporate development team, he was responsible for leading its corporate strategic planning and mergers and acquisitions activities globally. He was able to put his previous M&A experience to good use immediately, he recalls.