Journalists across the country go to great lengths to keep their distance from sources. It’s not that we don’t like the people we cover – many are pleasant enough; some could be friends in an alternate universe.

But we shouldn’t get cozy; we can’t. It colors everything else we do, beyond our control.

Of course, there’s room for judgment in how to interact with people we cover. My rule of thumb is “Friendly, but not friends.”

Friendly might mean saying hello, smiling, exchanging small talk.

Friends do more. They meet socially. They do favors for each other, maybe protect each other.

It’s hard to define exactly where that line is. But when I read this post on The Daily Call about journalists pool-partying with Vice President Joe Biden, I knew: This sure ain’t it. Kudos to Mike Riggs for speaking out.

Then, I read Marc Ambinder of the Atlantic make this ridiculous rationalization of journalists getting chummy with sources. I was disgusted and ashamed.

Is it a Beltway thing? Are Washington journos more likely to get so entrenched in people, places and institutions they cover, they don’t see the actual and perceived conflicts of joining, playing with and being them?

Riggs’ take on it is exactly right. There’s an allure of being both in the know and in on the fun.

Glenn Greenwald also had a good report. How can you read the giggly, fawning Twitter messages of CNN’s Ed Henry and not feel sick?

Getting a chance to see Biden’s casual side? Chatting about Helen Thomas? Squirting each other with a water gun?

For this, it’s worth jeopardizing credibility, independence, neutrality and integrity, all at once?

Good luck telling people to trust you – that your journalistic acumen can’t be swayed by a day of laughing and splashing with Biden and Rahm Emanuel.

It won’t work. You don’t dictate perception.