Discussing almost anything highly technical over the phone is usually a disaster. When's the last time you solved a production problem without reference materials over the phone? Sounds hard right? Whiteboards are a crap shoot - we can all come up with lots of problems that are difficult to whip up without any reference materials but what's the point? Neither method reflects how anyone actually does their job so get rid of it.

Every skill takes time to develop yet most people think they are good at giving interviews with zero experience, research, experimentation or methodology. Allow a typical junior employee to start interviewing candidates and it will go right to their head as they are given their first taste of power over others in a professional setting. It takes time to learn how to interview properly, figure out the specific attributes you want to screen for a particular role, remove your own personal biases and plain get over the fact that you have the power over someone else's career for probably no good reason.

My philosophy on interviewing is that as an interviewer you want to avoid screening for anything that is not reflective of the actual job duties and to also avoid anything that the candidate is expecting to be asked. If you ask typical programming questions then you are likely screening for candidates that have the most time to prepare for interviews which screens out the lazy but also screens out the no-nonsense doesn't like to waste time types. Ask questions that get to the core of what interests them and figure out if they will be motivated enough to learn what they need to get the job done. Then get back to them quickly!