It got FDA approval as a commercial sweetener, but remember that the FDA has approved many a food ingredient (even those that can not be called ‘food’ by any stretch of the imagination), that has proven to be detrimental to our health.
If the monk fruit is eaten as a fruit, it has wonderful health benefits. The tangle comes when companies extract compounds, isolating them from what makes up the whole food, and processing them into a commercially viable product. I am always curious why we think that an ingredient in isolation from its natural companions, is expected to perform as it did while in its natural state.
Well, there is still research that is needed before Monk Fruit extracts can be assumed totally safe. For now, use Mogroside (sold as Fruit-Sweetness) in moderation.
Below is the link to an article that appeared in the Chicago Tribune, which will tell you more: