Ten Questions about Confirmatory Assignments

There are certain recurring forms of agreement in the IP world that remain a bit of a mystery to me. Perhaps none is more puzzling than the so-called "confirmatory assignment." For my sins, perhaps, after a long hiatus, I encountered several versions of confirmatory assignment over the last month.

This got me to thinking about the why and what of a confirmatory assignment, assuming that the putative confirmation relates to an unwritten assignment of rights that took place at an earlier point in time. So what are my difficulties with a confirmatory assignment? Let me mention the following:
1. Depending upon the applicable IP rights and related law of contract of the jurisdiction, to what extent can an unwritten agreement validly assign IP rights?

2. Assuming that an unwritten assigment is valid, what is the evidentiary showing that is required?

3. Can one record an unwritten assignment on, e.g., the appropriate patent or trade mark registry? If so, what proof is required?

4. Is the evidentiary showing different in connection with establishing the validity of the assignment in the context of a transaction?

5. How can a purchaser receive sufficient comfort about the validity of the assignment, or is it a matter of risk allocation depending upon the positon of the parties?

6. Does the standard of evidence to establish an unwritten assignment differ once again in the context of a court proceeding?

7. Does the standard of evidence to establish an unwritten assignment differ yet again iin the context of taxation?

8. Is a confirmatory assignment a form of ratification?

9. If it not a form of ratification, what is the proper legal characterization for the agreement?

10. In light of all of the foregoing, does the confirmatory assignment confer any benefit to the parties, other evidentiary or substantive?
Any readers with thoughts about these questions are urged to share them.