...but I don't believe you HAVE to have a degree and I don't believe you HAVE to flight instruct.
In my experience, I both agree and disagree.
I don't believe you have to have a degree in our society IF you have a marketable skill and significant relevant experience. Flying, in its essence, is a marketable skill. As a software engineer, I have a very marketable skill, which, for better or for worse, has enabled me to put my last 30 college credits on the back burner in favor of accumulating flying experience. And as long as I keep that skill somewhat current, I'll have something to fall back on (or, a way to supplement my income).
On the flip side of the coin, I believe those last 30 credits will have to be a priority for me to be successful in my aviation goals; remember, all things being equal, what will make you stand out?
In IT, I stand out for most positions by having 10 years of desirable experience. If I were applying for a senior architect or managerial position, however, all the candidates would have the same 10 years of experience, and I would lose out by not having a C.S. degree that the other geeks probably have (not losing any sleep over that though...) When dozens of guys and gals are vying for a slot at a legacy, they all have thousands of hours of relevant experience. The ones without the degree aren't getting a phone call, because the other 97 have one. Now, you still have 97 on a level playing field, what makes one stand out?
To answer John's original post, no, you don't need a degree....depending on what your goals are. You can comfortably find a middleground and hang out there without one, or you can aim for the upper echelon with one. Look up the word "underemployed" to see what happens if you fall short. Of course, there are the Bill Gates' and Michael Dells' to provide the exceptions to the rules.
Oh, and a quick note to troopernflight: 4 years of getting up early? C'mon now, my first order of business as a college freshman was to schedule all my classes after lunch...