I’ve been juice fasting (juice feasting) too, not because overweight but because of other health issues and it’s great. I didn’t lose any weight at all since I was already on my “ideal” weight. However, for everyone that feels inspired, you need to do research first because you will start to detox and it will scare you if not prepared. Always do research! When you fast, water or juice, the body will start to try to get crap out of the system and if you have a lot of toxins in you, it can be pretty bad. If you feel too sick, you can slow down the process by eating whole fruits. Not hard fruits but the soft ones that doesn’t have much fibre in it. There are lots of good books out there on fasting.
To be clear, there’s a difference between juice fasting and juice feasting.
From what I understand, the difference is that juice fasting may or may not meet your caloric needs, while juice feasting involves meeting your calorie needs by drinking fresh-made juices. (Though, indeed, determining your caloric needs is another story.)
One thing both have in common is that they’re not intended to be long-term diet solutions.
I agree with what you say, though; detoxing has a place, but it’s wise to do it intelligently (like everything else, I guess).