For example, according to an (unverified) story someone told me, a vendor to US east coast food cooperatives now controls many of them; they get their person in, pass bylaws empowering them and disempowering the board (the board usually lacking sophistication), and have deeper pockets for any legal struggle than any co-op member does.
Also, I remember in the news that a non-profit or limited-profit company in the IT industry, founded for the public good, is going to be turned into a for-profit. The board actually fired the person behind this plan, but that person came back and fired the board members.