Doesn’t having a beer in the afternoon when you’re at work sound pretty cool? Sure it does — but that doesn’t mean it’s a good idea.

Drinking at work is apparently getting more popular, especially in Silicon Valley workplaces, Bloomberg reported March 13.

Companies like Crowdflower, Tello, Twitter, and Yelp all reported making alcohol in some form available to their employees on a fairly constant basis – in some cases, 24/7.

Twitter keeps its employee fridge stocked with nonalcoholic drinks, plus beer and wine. “We treat employees as adults,” said Twitter spokeswoman Jodi Olson, “and they act accordingly.”

Tello’s CEO, Joe Beninato, said, “When you’re working at a startup, you’re working 24/7 and it takes over your life. It’s not like it’s a wild fraternity party or something like that — we’re all adults.”

At a recent office celebration, he said, “We got out the whiskey, and everybody had a shot.” And that was before noon.

“Alcohol is sort of a slippery slope, because obviously you’d think it might impair their performance,” Dalton Conley, a social sciences dean and professor at New York University, said. “Many people can work after one beer, but I doubt many people can do serious knowledge work very productively after four or five.”

Furthermore, there’s always employees who can’t stop, or behave well when they drink, according to Robert Sutton, a professor in Stanford University’s management science and engineering department.

That’s not all. “There’s like a bazillion studies that show when people drink, their performance is impaired, and there’s problems with absenteeism,” Sutton said. (Not the most authoritative quote, granted, but he’s right.)

Then, too, researchers have found that when men drink in the workplace, women are more likely to be sexually harassed. A 2004 Cornell study, sponsored by the National Institute on Alcohol Abuse and Alcoholism, determined that “harassment incidents increased more than twofold for each additional alcoholic beverage consumed by male co-workers,” Bloomberg reported.

To its credit, Yelp requires that employees don’t get to help themselves to the free beer unless they show their badge to an iPad app that tracks their drinking.

“If you’re at the top of the leader board consistently, I don’t know if that’s a place that you’d want to be,” said Yelp’s director of consumer and mobile products, Eric Singley. “Luckily, that hasn’t really even been an issue.”

Personally, I’d hate to see this trend spread, because drinking at work simply isn’t a good idea in most workplaces. It might work just fine in a small workplace like Tello, which only has five employees, where the risks aren’t that great.

But I’ve worked for some large organizations with thousands of employees. I can attest that even though they were alcohol-free workplaces, there was still a high number of employees whose performance was subpar (and sometimes nonexistent), and an astonishing number of situations where employees displayed judgment so bad it would make your jaw drop — and they did this while stone-cold sober.

Don’t believe me? Just ask anyone who’s worked in human resources in a large organization why their organization doesn’t allow their employees to drink. They’ll turn away with a shudder.