Short Answer: If you are trying to lose weight, yes.
When trying to lose weight on a ketogenic diet, it is absolutely possible to eat too much fat. Remember, as much as we talk about the importance of lowering insulin production to keep our bodies from storing fat, you still have to consume less calories than you use to lose weight. The ketogenic diet isn’t a magic trick that bends the laws of physics, it just makes consuming too many calories a much more difficult thing to do.
However, if you are at a healthy weight and are using a ketogenic diet for therapeutic purposes, the answer is not so simple. Different metabolic problems respond differently to the higher levels of ketones produced by a diet with a higher percentage of fat. For instance, epileptics have been put on diets where up to 80% of their diet is fat in order to control seizures. And I have heard people with cancer report how they find greater success with a fat intake north of 70%. (In case you are wondering how they do that, the woman I heard speak says she takes jars of grass-fed butter blended with herbs with her everywhere she goes and puts it on anything she eats.)
So if you are trying to lose weight, fat should be a high percentage of your calories but total calories should be low enough to cause weight loss. If you are trying to keep a particular medical issue at bay, the higher your ketone level, the better.
Any questions? Leave them in the comments below!