My initial communications were with the Youtube/Google recruiter. This particular recruiter specialized in UX roles.
Following the this initial phone screen, I had a 30 minute phone interview with one of their senior UX staff. I started be briefly describing myself and my background. They asked me to describe a project that I had worked on and how it relates to work that I would do at Youtube. As I described the project, they asked more detailed questions about the specific methods and techniques I had used. They also posed a design problem to me and asked how I would design a UX research study to address it.
About a week later I got email from the recruiter inviting me to an onsite interview. Part of the onsite interview is a 40 minute presentation. The recruiter send me a document describing what they were looking for in the presentation and some tips for being successful.
On the day of the interview, I gave the presentation first. I presented in a small conference room with about 4 people in the room, and about four other people at two remote sites who participated via video-conferencing.
Following the presentation, I had several 1-on-1 interviews scheduled.
Everyone I spoke to at Youtube was very enthusiastic about the company. They mentioned how smart their co-workers are, and that they liked the fast-paced startup-like environment at YouTube which seemed to contrast with the more bureaucratic atmosphere at the Google campus in Mountain View.
Overall I found them friendly and smart. I got a lot of good (ie hard) questions during my presentation. The questions during the interview and during my 1-on-1 interview were straightforward and focused on my past experience, the types of projects I had worked on, what methods I used, and what the outcomes were.
Though I liked the people, overall it was not a great experience. Halfway through my interviews, all of the UX staff got called to an emergency meeting, and I was told that they would have to reschedule the rest of my interviews. It took me a week to hear back from them, and when I did hear back I was told that the position no longer existed.