When do you believe "anonymous sources" and when don't you?

Sometimes yes, sometimes not. Take it with a grain of salt.

Named sources lie (Trump, Sanders, Pence, etc.), so just because you are named doesn’t make you truthful.

My guess is that on average, an unnamed source is more likely to be honest. He may still have an axe to grind, but is probably telling the truth.

At the present I would hesitate to believe any anonymous source of any information.

In today’s world, I would trust “anonymous sources” quoted by groups and/or publications that have a longstanding and verifiable history of fact telling. People stay anonymous in this climate in order that their families and themselves are not threatened and attacked by angry crackpots because they don’t agree.
Ford had to move because of credible threats during the Kavanaugh hearings.

I believe “anonymous sources” when many of them say the same thing.

Depends on the source.

Never. I believe none of the “news” being fed to us is absolutely true. Everything is tainted left or right.

No I don’t.

People have to be anonymous sources because harassment and sometimes murder is a reality for people that tell the truth.

People in power have resources and means to harass those that go against them.

Despite the beliefs of others, a person’s life actually matters and it shouldn’t be ruined for telling the truth.