I got an email fairly quickly from yelp, wanting to set up a phone interview. I wanted to get into the mobile development section of their software engineering team. The interviewer was a female, and she said that even though I was applying for the mobile developer position (iphone/idevice) that they had already hired people for that position, but continued the interview anyways saying that I might fit into one of their other departments (like back end server). She was friendly, and seemed to know what she was talking about, if not she had a very thorough piece of paper in front of her. She said that they are completely unix/linux environment, so know your unix commands (I didn't which is probably why I was declined) She also said that they code primarily in python, so i would guess be prepared to know that. Since I am mainly a mobile application developer, I don't have much experience in python. She asked how you would find the number of lines in a file, or how to find the processing power of a particular program. Another question asked about how a domain name gets mapped to a server on the internet (didn't know that one either). The only reason that I rated the interview as difficult is more than likely due to my low level of skill in topics that are outside mobile development.