Poor communication. I literally had to call the recruiter once to ask when my 3rd interview was scheduled. All she said was, "It's today. Didn't you get an email." Then ten minutes after I got off the phone I got an email. I still haven't received communication saying that I didn't get the job, but I assume after a month, I would have heard something. Although, I've been told their hiring process is extremely long and laborious.
The whole process consisted of: a phone interview with hiring manager, then two on site interviews with direct reports, peers, the hiring manager again and multiple VPs (many interviewers).