The problem I've found with too much sugar in a rabbits diet is that you probably won't know that your rabbit has a GI problem until they actually get GI stasis, and then it might be too late. My first rabbit that had it, died within 2 days of showing symptoms. I had no idea she had sugar problems, so I fed her a very little piece of fruit, and the next day she was sick. Unless you understand all the warning signs of a possible digestive problem, and are very very observant, you may think you have a healthy rabbit and feed it treats as if it were healthy, and then before you know it you have a sick rabbit. I've read several posts by people that thought they had a perfectly healthy rabbit and all of the sudden their rabbit was sick with stasis. I'm by no means saying no treats for rabbits, but that GI stasis can happen unexpectedly because of the rabbits diet, and if you have ever had a rabbit with it, you know there is good reason to be somewhat cautious. So yes, sugar and calcium aren't a big deal a lot of times, unless it's your rabbit that happens to get sick.