The other day I walked past an office building very late on Saturday night, after midnight. Even though there wasn't anyone inside (since Friday afternoon!), the lights were on in most of the windows, and I could see through the glass doors that the escalators were going and going, carrying nothing but air between the floors all day and all night. Also, the lobby was all lit up and the fountain was on. I'm willing to bet that most of the computers were also on, and that the thermostat isn't set for different temperatures during the day, night, and weekend
On a different level, a day earlier I noticed another wastefulness. I am a blood donor - I don't get money for it, only a few bars of chocolate, but that's not why I do it - and it is hard on me when I realise how much waste is generated. All of the bandages, needles, bags, tubes, etc., are disposable, and since they are treated as medical waste, they don't get recycled. Unfortunately, even things that don't actually come into contact with blood (clothes and shoe covers, for example) also get thrown away with the medicals.