Self-scouting is a tool used by football coaches that helps them discover tendencies in their team... weaknesses that can be exploited by their opponent. Self-scouting is a helpful tool for preachers too. Studying yourself as you preach will be eye-opening... helping you identify those nervous tics, oft-repeated/overused words, distracting gestures, poor grammar. The more honest you are in your evaluation, the more helpful it can be.
However, there ARE dangers to self-scouting too. Here are 4 of the most obvious:
1) Perfectionism - You will never be perfect and you are going to frustrate yourself and those who follow you by being too hard on yourself. Perfectionism will ooze out of your pores when aren't even aware of it - image will become too important - you will call your observations of others "honest," but the people around you will see you as "harsh."
2) Myopia - You might become everything you think a preacher or leader SHOULD be, but your perspectives might be entirely wrong. If you think a "good preacher always does THIS" then you will also do it (even to your detriment.) You will establish habits that are difficult to break. Your methods will become stale and uninteresting. You will be critical of others who are highly effective and miss out on necessary change.
3) Discouragement - You can be so hard on yourself that you constantly need the affirmation of others to prop you up. That neediness is wearisome to those who follow you. Self-preoccupation is counter-productive to ministry because NOT EVERYTHING is about you - but it will seem that way if you are always measuring yourself. Failures will be blown out of proportion (and so will victories.) That roller-coaster you are building for yourself won't be fun.
4) Pragmatism - results can become an insatiable idol that will lead you to down the shady-lane of hypocrisy.
Self-scouting can be likened to other good things (like exercise or dietary supplements.) In moderation, those things are good for you. But if you don't believe you can have too much of a good thing, try fiber :)