I weigh daily. I am never concerned if I have a sudden 3 pound gain, but I'll be concerned about slowly creeping up. A sudden 3 pound gain is almost certainly water retention due to increased sodium or whatever. But if I am slowly creeping up, that will demand my attention. And if I don't weigh daily, I don't know if that 3 pound gain is a weird water anomoly or lack of vigilance. thus, daily. I also know that I bounce around a pound regularly (like I was 144.8 a few days ago, then 145.8, then 145.6, then 145).
I'm in maintenance, but I weigh twice a week. I became obese by avoiding the scale so that I could avoid the truth about my weight. I don't do that anymore. I don't need the constant input of daily weighing, how my clothes fit is usually good enough, but twice a week makes me have to deal with a finite number that is a direct result of the choices I've made.
I weigh daily. First thing in the morning, after I've "bathroomed" and before I have breakfast. I consider that "my true reading". I take into consideration those goofy aggravating fluctuations from my monthly interference and whether or not I had a bit too much salt at dinner time the day before, etc. But it keeps me on track.
I'm a happy daily weigher. It's not an obsession at all, but rather the absolute best way for me to calculate how many calories I actually eat and burn, based on the scale's response over time. It keeps me accountable and removes the power of the random number generator, all at once.
Artic Mama I agree, it isn't an obsession. It's a tool. I used to think it was wrong to weigh more than once a week but then I read a study that showed people who weighed daily were not only more likely to lose the weight but also to keep it off. I don't weigh daily but I'm not afraid to weigh several times a week now.