Phone interview -> in person interview -> in person interview -> founder interview. Standard non-programmer tech questions. Less focus on brain teasers and more focus on reading and understanding data (they brought in papers with charts for me to read and interpret). The (last) founder interview actually has a fairly low pass through rate, so don't think that meeting the founder = offer. Only problem was entire process lasted a few months for me - you need to stay on top of the recruiting department (through your referrer most likely) to keep the process moving quickly.

I applied online and received a phone call a few weeks after I applied. The whole process took probably around 9 months-- many, many interviews, usually around 8PM EST, with various people. In total, I had about 8 interviews, not including the final site visit. Each of the interviews were a little draining, consisting of about half an hour of getting-to-know-you type questions to determine if I was a jerk (their words) and then half an hour of engineering questions. After months of phone interviews, they flew me to Palo Alto, where I had a full day of interviews with a variety of people, to include lunch with potential co-workers. The final two interviews of the day were with the two founders.