lying is fun, you can say whatever you want! i recommend you all try it out in moderation

Depends.
Your fellows? None at all.
The State? Misinformation

I think the state in this case needs to be divided into adversarial and non-adversarial departments (or subdepartments). It’s better to tell (for example) the water department you don’t know whether the pipes are lead if that’s the case, rather than forcing them to unearth copper pipes or letting them leave lead pipes.

But it is absolutely appropriate (assuming you believe in strong rights to privacy) to insert NSA keywords into benign communications, so that NSA wastes time on your false positives, but that’s because NSA isn’t supposed to be doing mass surveillance of the public, rather is supposed to be helping develop communication security that is impervious to surveillance.

If your local precinct actually works with the community, doesn’t harass minorities and doesn’t rob civilians via asset forfeiture, it might be worth giving them sound information (including saying you don’t know what you don’t know.) On the other hand if it behaves typically for law enforcement in the US, leading them to chase geese will save everyone else trouble.

Oh man I feel this when people ask for directions. Because I know how to get somewhere, but I also forget a lot of steps along the way.

None.

When a man lies he murders some part of the world.

– Merlin (Excalibur, 1981)

If you know something to be false and try to pass it off as truth, that is lying. It doesn’t matter how you phrase it or try to hide behind symantics like “I’m just asking questions” or “it’s just a hypothetical”.

That being said, it does not mean that you cannot contribute to a conversations if you are not an authority on a subject. If you are not sure or cannot recall a credible source for your information you can preface your comment with something like “I never confirmed the validity of this, so I may be completely wrong, but…”.