Is cubicle etiquette an oxymoron?

FORTUNE -- Dear Annie: Am I the only one who wonders what ever happened to good manners? I'm not even that old (37), but it seems to me that people used to make more of an effort to be polite at work and practice certain basic courtesies. Now, it seems the workplace has gotten so casual that anything goes.

Here's an example: At my company, only the very top people have offices with doors. The rest of us, including middle management types like me, work in cubicles. But I frequently need to concentrate on something complicated or have a difficult conversation with someone, and it's hard to do either of those when people feel free to barge in at any moment without even a pretense of "knocking" first.

Most of the coworkers who do this are younger than I am, which leads me to think that plain old good manners are an endangered species. Do you agree?

Also, what do you think of people who use the "bcc." (blind copy) feature to secretly send emails loaded with "constructive criticism" to other people's bosses? Some of my direct reports seem to see nothing wrong with this, but I think it's dirty pool. --Seething in Seattle

Dear S.S.: It goes without saying that every generation (including the one preceding yours) tends to view the next as a horde of barbarians at the gates, but you might have a point.

"People's manners in general really are getting worse," says Vicky Oliver, author of 301 Smart Answers to Tough Business Etiquette Questions. "It's partly because of reality TV. Being obnoxious has become the new norm."

This shift seems to be compounded by technology. In her business-etiquette seminars, Oliver often hears the complaint that "young people now are so used to multitasking that they don't seem to realize that, in a face-to-face interaction, it's rude not to pay attention to the actual person who is right in front of them."

Paying attention to the person who is right in front of you is the essence of manners, of course, and it includes noticing that person might be too busy to deal with whatever your problem is.

To discourage pop-ins, Oliver says, "keep your hands on your computer keyboard and start typing furiously. 'I'd love to chat,' you could say, 'but this report is due in an hour.'"

If that's too subtle, even after the umpteenth time you do it, then be direct: "I do want to hear what you have to say, but right now I'm tied up. How about if I come by when I'm finished here?"

Talkback: Do you agree that manners in the workplace have gotten worse? Leave your comments at the bottom of this story.

Of course, the interloper may well be busy with something else by the time you get over there, and then you'll be the one barging in, but in that case, you can set an example by quickly backing off and making an actual -- gasp -- appointment to get together later.

As for the "bcc.," you don't say whether you're the recipient or the victim, but either way, Oliver agrees with you that undermining a colleague by tattling to the boss in a blind email is sleazy.

"It's dangerous," she says. "Write a seemingly constructive email while blind-copying someone's boss and you are engaging in e-war. You may be able to get away with it once or twice, but eventually blind-copiers get a reputation for being sneaks and weasels."

Take our business etiquette quiz to see how your office manners stack up

Point out to your clueless underlings that becoming known as a sneak or a weasel is not good for anyone's career in the long run. In fact, be prepared to explain other "basic courtesies", as you call them, whenever it seems necessary. If you can summon up the patience to do it, and keep a grip on your sense of humor, you'll be doing your direct reports a huge favor.

"Young people are often in a hurry to change things, but no one can change the rules without first understanding what the rules are," Oliver says.

Rule Number One, she says: Treat other people the way you would like them to treat you. Or, as Google's unofficial motto has it, "Don't be evil."

Oliver says that a key point to convey to your coworkers is that "in this economy, with everybody putting in such long hours, you'll get farther if people like working with you. To some extent, success really is a popularity contest."

Talkback: Do you agree that manners in the workplace have gotten worse? If you've figured out a way to politely minimize unwelcome interruptions, tell us about it on Facebook, below.