Hello again David, thank you for your excellent post about one of my favorite subjects.  The three mistakes you cite by those who delegate are wonderful additions to those I have always embraced.  The one that resonates most with me, as it seems to have with Gord, is 'Accountability'.
It is my perspective that ALL companies would benefit by embracing and implementing the concept of accountability as the foundation of its daily operations.  Accountability, in its simplest form is getting everyone in the firm, from the top-down, to 'pull in the same direction'.  That can only accrue to greater effectiveness and efficiency; two components that play a huge role in any company's long-term success.
Stephen R. Covey, in his best-selling '7 Habits of Highly Effective People', includes a chapter on Delegation.  Covey separates the process of delegation into two categories: 'Gopher' and 'Stewardship'. Rather than take the space to explaain, I would encourage anyone who has not read the book to at least look at this section to get Covey's full insight on the topic.  It made a huge difference in my management approach to this critically important process and its inseparable connection to 'being willing' to be held accountable for whatever our assigned responsibility is for the work to be done.
Respectfully,