Cochrane reviews are good for looking at this kind of stuff. These are high-quality meta-analyses of the available data on all kinds of medical interventions. The Cochrane Review on Anti-oxidant supplements is particularly interesting. It concluded that "Vitamin A, beta-carotene, and vitamin E may increase mortality."

So taking vitamins (or at least vitamin A or E) without any particular need for supplementation may actually be bad for you. There's poor evidence for the use of many other vitamins for people who don't have any particular deficiency.

Tech support stories like this always strike me as kind of pathetic. I get the need for people in retail to let off steam about rude or just plain inconvenient customers. If you're in retail, your job is to sell stuff and those kinds of customers take up more of your resources and prevent you from doing your actual job.

But if you're in tech support the people you're supposed to be spending your time on are the people who have problems with the service you're supporting. And these people are, by definition, not as able with technology as you (whether in terms of knowledge or access). Making fun of these people shows a contempt for the customer that reflects much more poorly on the teller of the story than its subject.

Anyhow, the real problem in that story isn't the dumb customer. The real problem is this: "I look up her password and use it on the site to make sure it
works." The website, whatever it is, is evidently storing people's passwords in such a way that its employees can see (and use) them. That's a truly awful idea and a security breach waiting to happen. That isn't the support person's fault, but it's a much better target of derision than the customer - unlike customers, the people who designed the website are supposed to know what they're doing.