Well, obviously as a Michigan fan I'm ok with this. But at least two of the people hired by Harbaugh are coaches. Partridge and Bush (assuming he is hired) were HS head coaches. They both started at a team that was nothing, built it up, won the State Championship, and were hired by Harbaugh. If he was hiring guys who had no background in football, it would be really skeezy. These guys were very successful. In fact, Bush Sr. played at FSU, then in the NFL. He coached in HS, now moving up to College ball. This is a guy who has been around. You'll notice that on Michigan's incoming recruits, Bush was decent, but there were lots of better recruits than him. Harbaugh didn't hire any of their parents. Harbaugh is hiring guys who he sees being a good fit for the team, and guys that help open a pipeline.
I just read an article on how prevalent hiring HS coaches at college programs is in Texas. In fact, Hermann has a guy on his staff who was a HS coach, and who was the key to signing the number 4 player in the country. (My facts might be off: maybe one of you from Texas can verify). The point is, it makes lots of sense to hire young, driven, successful High School coaches.
I fully expect Harbaugh to continue to do this. Oh, and there's one other coach out there who's son came to Michigan: Tyrone Wheatley. So there are three on staff whose kids came to Michigan, (Bush, Bush, and Wheatley) and two others who came from HS ranks. (Partridge and the guy from St. Ed's). Regarding Partridge, he was promoted to LB coach when Durkin left Michigan for Maryland. Assuming Michigan loses another coach or two when they take a higher position elsewhere at the end of the next season, Harbaugh will look to a successful High School coach to join Michigan. There was scuttlebutt that he wanted to bring on Poggi, the former head coach at Baltimore Gilman, whose son plays for Michigan.