I caught up with Louis in email, and got a chance to ask him a few questions. Here's the interview:

Why did you leave eBay?
It's been four years, during which I have done many things for eBay. For example my new search engine has been kicking butt for about two years; it's perfectly adapted to eBay's needs and is in the same league as Google in query volume. In return eBay gave me a fancy Fellow title and a corner conference room. I got to play with all sorts of large problems and see the solutions used by millions of people, exactly what I like to do. So I'm leaving in great terms.

The main reason for me to leave is that eBay does not absorb innovation at the pace I enjoy, and its focus is narrower than Google. So rather than chewing on variations of e-commerce for the next few years, I'm very tempted to play with radically new stuff: satellites images, machine translation, ways to extract knowledge from giant bodies of data ... who knows what else? And frankly, I'm dying to peek under the hood and see the infrastructure they have created. For someone like me, it's the ultimate Christmas toy.

By "your new search engine" I assume you mean the internal search at eBay, right? Can you tell us a bit more about that?

Sure. We replaced the search back-end a couple of years ago with home-grown code, and it has been performing very well. The only user-visible difference is that any change (price, new item, ended item,...) is reflected in the search and browse pages in real time. So it was not a traumatic user-interface change, just a better back-end.

Did Google recruit you?
I have known Larry and Sergei forever, I want to believe that I had a standing invitation. All it took was one email to Larry.

What might you be doing at Google? Will you be working on ecommerce?
The agenda is "Whatever I want", which is really attractive. I honestly don't know because I need to check what is going on, all the projects, the strategy, and the infrastructure. I have been working on search for e-commerce for several years now, so a change would be welcome. The Froogle rumors are a bit hasty given that I have not made up my mind, and I won't for a few weeks. Someone must have connected the dots in the obvious manner, but I am tempted by more exotic stuff. We'll see.

Really, no remit at all? No expectations? Who are you reporting to?
Nope, and again, this is a big part of the attraction. I don't know who I am reporting to. I think I need to pick my boss as well as what I want to do. How can you say no to this? :)

What are you most interested in right now in the field of search?
Just to be clear, I think that Google has plenty of search experts, so I may actually never touch search. But since I have the mike in hand, what I find the most interesting problem in search is to think of it as a dialog rather than a one-shot thing: enter query, get ten links back. The search engine needs to do its part to keep the dialog going. That's what I said at Web 2.0 last year.

What problems are the most interesting?
I'm fascinated by the many ways we can extract real knowledge from billions of tidbits, whether they'd be Web pages, queries, links, reviews, social networks... We have a few tools today, mostly statistics to isolate repeating data from the noise, but I think we will eventually go much further. What we need are generic pattern recognition engines. It ties into what Jeff Hawkins is talking about on the structure of the neocortex.

Does this mean you have to give up your "ALTVSTA" license plates on your car?
Nope, I'm too proud of this baby. Remember, AltaVista was a huge technical success, for which I take some credit, and a business disaster for reasons over which I had no control. Being stuck inside a dinosaur in a death spiral (Digital) never helped. The portal strategy of the barbarians from Houston (Compaq) and the lack of focus on core search made sure that any remaining value was destroyed. Google was simply a better tool that filled up the space, more power to it!