There are certain topics that are independent of any particular appraisal method. One subject that comes up often is the objectivity or subjectivity of various appraisal techniques. For a full examination of this issue look at this page.
Another subject of great controversy is the application of appraisal discounts and premiums. My views on the so called lack of marketability discount can be found here.
Finally, the subject of covenants not to compete has become somewhat of a topic of controversy in certain jurisdictions.. My views on this topic can be found here.