Okerstrom continues to have an impact, most recently by identifying the strategic areas where Expedia must excel in order to continue to grow.

What was it like to work inside a corporation for the first time after leaving professional services?
I was a little bit nervous about it. Corporates often have a reputation for being slower paced, with a lot of 9-to-5-ers. Expedia wasn't like that. It was filled with people who had done things like I had done, and were very much like-minded. They wanted to make themselves better and constantly learn. It was a pretty easy transition for me.

You're currently CFO, but also still have a great deal of interest in and responsibility for corporate development. How do you find that combination of roles?
I find it incredibly fun, to be able to think strategically and then as CFO to be able to actually put that strategic thinking into practice, through controlling, with the CEO and the board, the capital allocation decisions. To make sure we effectively put those strategies into place is very rewarding. It helps me marry the short-term versus the long-term view.

What's an example of that thinking in action?
The TripAdvisor spin-off is a great example of that. TripAdvisor was a business that continues to be very fast-growing, and it was a business that we really liked having. If you only took the very short-term view of Expedia, you might not spin it off. It was really driving a lot of our growth and driving good quarterly performance for the business. But we, and our board, had the ability to say that the long- and medium-term prospects for Expedia are strong on their own. To the extent that we suffer some short-term volatility, that was a very acceptable trade-off to make.

What was the most challenging aspect of the TripAdvisor spin-off?
Just the decision to do it.

You've identified six strategic areas for Expedia to focus on going forward, including developing across geographies; expanding rapidly in the highly fragmented hotel industry; making technology platform investments; achieving success in new distribution channels; and creating powerful cash flow generation. Can you tell me about the process of identifying these areas?
We took a look at our $1 trillion travel industry, and realized we do just over $30 billion in travel bookings. We're the largest travel company in the world, and we've only got 3% of the market. That's a huge amount of opportunity in front of us.

We really thought about what it is going to take for us to win in this industry, to take 3% in market share and make it something much more significant. It really boiled down to a few things. One is that the bulk of the value in the online travel industry is in the hotel industry, because you've got hundreds of thousands of small hotels that can't necessarily afford the marketing reach and the technology necessary to reach the traveler in Japan who wants to come stay in Rome. We can do that for them.

It's all about geographic expansion. It's about showing consumers around the world the hotels we already have, in the U.S. and in Europe, and adding new supply. If you can build the biggest network of consumers on one side, and all of the geographies and hotels on the other side, that creates something very compelling for suppliers, for consumers and for the industry as a whole. Geographic growth is a core part of it.

And all of this is enabled by technology. Expedia created an industry on the back of technology. We recognize that for us to continue to have a leadership position in this industry, we really need to maintain that, that technological edge. The most accurate rates and inventory, the fastest Web sites, translated perfectly in every language. We need to invest in that, in order to win.

Lastly, as consumers move to new distribution channels like mobile, we need to be in a leadership position there as well.

It's a huge industry. The three things that are really going to drive us are geographic expansion, technology and product investments, and really being the best as new distribution channels emerge. This is a very attractive business. It can be hugely profitable and can generate a huge amount of cash flow for shareholders.

Finance-wise, are there any special initiatives that have gone along with the strategic imperatives?
As we expand geographically, we have put a pretty significant focus on our foreign exchange operations. We've got a great team who have built up a great FX hedging program. They've done a terrific job. We're able to pretty nicely control the economic risk associated with foreign exchange.

The other focus for us more recently has been around building out the financial infrastructure to be able to support the global platforms. We've been essentially rewriting and implementing a new ERP system. They're tough things to do, but it's something we needed to invest in, and implement.

The third thing is that we've announced recently a pretty significant initiative whereby we're changing the way consumers are able to book hotels on our Web site. Consumers have only been able to pay us directly with their credit card, under the merchant model. We're beginning to introduce Expedia travel preference [an agency model], where consumers have a choice. They can pay us up front or pay hotels at the time of stay.

How did you manage through the economic downturn?
You've got to be pretty disciplined around your cost structure, and we were fairly effective on that front, especially on discretionary spending items. But the great thing about the travel industry, especially online travel, is that we're somewhat countercyclical. Consumers like to travel. They will scale back, but they still like to travel. For example, in Europe, where there have been significant economic challenges, they still take their vacations and still like to travel.

What do you think is among the most important lessons you have learned along the way?
It's about pushing yourself. One of the things I say to young people whom I mentor is you need to get comfortable feeling uncomfortable. Once you get comfortable with that feeling, it empowers you to take on new challenges. For example, you're never a public company CFO until you are. No one is experienced doing analyst calls, for example, or investor days. You just don't do that unless you're a public company CFO. The thing that prepared me best for that is that comfort in knowing that it's going to be uncomfortable for a bit. You'll get more comfortable over time, with experience.

What is the most challenging part of your job?
The most challenging part is keeping up with the travel. Expedia has operations on every continent, and some pretty significant operations in a few places. I've got a wife and two kids [5 and 9], and it's sometimes tough to be on an airplane all the time.

Have you had mentors?
I've had mentors along the way. I think it's incredibly important, and I try always to mentor people informally. Also, I have always tried to work for people I admire, and that's very true for Dara Khosrowshahi, our CEO, and for Barry Diller.

For the complete 2012 30 Under 40 list, see Ascending the Corporate Ladder. For last year's list, see Ready to Take Charge.