When I started my lab I had a very distinct idea of the type of PI I wanted to be. I had experienced some different styles and observed many others. I knew what my needs were as a graduate student and a postdoc and recognized gaps in what my mentors had provided for me. Above all I thought I could navigate that line between friend and boss where all my trainees would both respect me and want to hang out with me.
Oh, and I wanted to ride a unicorn to work every day.
I'm soon to finish up my sixth year as a PI and have mentored two cohorts of students at this stage. I'm hardly a grizzled vet of the mentoring game, but I've had enough experience to change my views on my role. There's been a discussion on twitter recently about whether someone is a Mentor or a Boss. It's a false dichotomy. An effective mentor is both. Sometimes you can spend your time leading your people in the general vicinity of water and sometimes you have to hand them a cup and tell them to drink.
When I say that I often hear people tell me "Well, my advisor was totally hands off and it helped us be independent and successful!" Whereas I won't dispute that many people can do well in that environment, it's often convenient to leave out the long list of those who flounder in those conditions and spent years of their life without advancing their career goals.
There are times when certain things need to get done for the lab and trainee alike, and there are times when the fostering of independence yields tremendous results. To pretend that a PI never has to act like "a boss" to make sure the bills get paid and the science gets done is a ridiculous view of how a lab functions. If a student comes in with all their own funding, then they can be free from the lab's reporting, publishing and proposal writing needs. Otherwise, as the lab goes, so does one's opportunities.
I still care that I have a good relationship with my people. I still hope that they like me and that we can sit down over a beer and enjoy the time spent together. But I'm far less concerned about blurring the line between the personal and professional relationships. I want to put them in the position to succeed at doing whatever it is they want to do, while advancing the lab's overall agenda. If that sometimes means pushing people to get certain things done, so be it.