I think the purpose of this technique (if you can call it that) is to express to the listener/viewer that you (the speaker) know that this question may be aimed at your discussion/speech/lecture/etc. and you want to save time by answering it before it is asked. But you can see how presumptious people can get with this: “Would I accept a hundred dollar bill from you? Absolutely!” I think effective speaking cuts two ways: a) people need to orate more dynamically and emotively, but b) even Max Headroom could orate more dynamically and emotively if he were so programmed. My point is, they (sc. rhetorical questions answered by the one who proposed it) should be used sparingly. But, where does one draw the line?? Honestly, I can’t answer thatquestion.

[NB—When using a question the asker is going to answer, I find it less confusing if the question ends in two question marks. One for the sentence being interrogative and the other for the question being interrogative; i.e., “are you asking this question”?]