These questions got me thinking about how we as a society look at being "fat." BMI does a good job of assessing populations as a whole, but I'm uncomfortable with the idea that height and weight are enough to give a good picture of an individual's health.
Because I'm very much on the small side, people feel comfortable casually saying something like "you can't weigh more than [x] pounds" or "you must weigh about [x] pounds." That number is almost always a good ten pounds less than I actually do weigh (which is a lot at my size), and when I tell them my weight, the response is genuine shocked disbelief. I don't think it's entirely a matter of people just being bad judges of weight because I've known some women with the same height and weight measurements, and clothes that fit them are pretty baggy on me; I just take up less space in general. The women I know who are closer to my size really do tend to weigh 10 pounds less than me.
That's because I'm sitting at 17% body fat right now, and I've got a fair amount of muscle (for any guys out there, that's pretty low for someone with a female body). BMI would put me in the same "healthy" category as the women who are larger than me rather than the "underweight" category the women my size are in. Whether or not you think that is accurate depends on your definition of healthiness. If you define it in terms of female fertility, I'm in the underweight category and might need to gain some fat if I wanted to get pregnant. If you define it in terms of strength and fitness, I'm in better health than either group. In fact, there are very few other measures where I'm in the same category as most people my weight. All my BMI tells me is that research has determined that, on average, people my height and weight tend to have body fat percentages and general fitness levels that are conducive to long-term health. But I'm apparently not average.
In these questions, it seems unlikely that these people couldn't benefit from losing some weight, which is why this isn't under Reader Response. The questions just brought up my issues with society's obsession with weight instead of with the level of fitness and healthiness that weight and BMI present just one small aspect of (and reignited my frustration with people guessing my weight and being very wrong).