While I understand the concept - I have never been quite comfortable with the ease that many people accept a guru or spiritual master into their life. Some have explained to me that it is part of the practice to surrender your growth to the master who knows better than you the journey... surrender without questioning - probably something I am not good at.
I wouldn't call her a guru nor is this about spiritual matters - but I can begin to understand the trust you can place in someone as your guide through a journey that is new to you and that they have been through with many others. My thesis advisor is proving to be a guide in more than just my thesis; it is also a lesson in surrendering (a bit) to someone and letting them guide me through the process without having to question or rebel when they say "what you need to do next is"... it helps that she gives really 'good' (meaning ones that are congruent with me) reasons for her suggestions. But my trust in her comes from the fact that it is a very new path to walk for me (this writing a thesis of 30,000 thing) and I need her guidance. It is a lesson in being able to accept help, guidance and to need another.