One of the most grievous offenses in the office is the impromptu meeting that somehow takes place at the admin's desk...and doesn't include, involve, or interest the admin.
(I say "admin" because that seems to be whom these offenses tend to fall upon, but really, this example could be anyone at a desk, in a cubicle farm.)
Here's how it usually goes: Workers A, B, and C somehow find themselves together in a cubicle aisle, realize they need to discuss the all-important TPS Reports, and congregate wherever they happen to be -- which is usually beside or in front of another co-worker's desk. Then they yap for 30 minutes about the cover sheets on the TPS Reports.
Guess what--this disturbs the Desk Dweller (and probably others around her) who need to get work done!
Now, the simple etiquette lesson says that Desk Dweller, who has committed no rudeness of her own, should say, "Excuse me, I need to get some work done. Would you mind taking the conversation elsewhere?"
And it sounds good on paper, but let's add a few real-life factors into the scenario:
Worker A is her boss.
Worker B is her boss's boss.
Worker C is the VP above both of them.
Desk Dweller has been holding her breath for a promotion for the last month, and doesn't want to piss any of them off. She also works in a button-down company where speaking up for yourself will delay that next promotion by a good two years or more.
So, hardly an ideal scenario. The snarky side of me wants to say that Desk Dweller should then get on an imaginary phone call and begin to discuss imaginary rectal exam results with her imaginary doctor.
Best solution: Don't have cubicleside meetings. Yes, I know your company is pressed for space and no one can get a conference room. Grab someone's empty office. Go down to the coffee room. See (actually try and see) if a conference room is free for 10 minutes, and go gab. Go to the cafeteria. Take off and hit Starbucks.
But please let the poor admin and her brethren get some work done.
Remember: a key to good etiquette is to think of others around you. When you demonstrate respect for others, you're demonstrating respect for yourself.
Now get back to work. And finish those TPS reports!