> the location of the stop sign defines a line perpendicular to your lane and you're supposed to stop completely before this imaginary line. Almost no one knows this is the law.

I am inclined not to believe this. I have been told by a traffic cop before that if there is no marked stop line or crosswalk, there is no legally defined point where the stop must happen: it's just a "use reasonable judgment" kind of thing.

That was in NC. The following is apparently a quote from a statute in Washington State that contradicts your statement:

“every driver of a vehicle approaching a stop sign shall stop at a clearly marked stop line, but if none, before entering a marked crosswalk on the near side of the intersection or, if none, then at the point nearest the intersecting roadway where the driver has a view of approaching traffic on the intersecting roadway.”

Can you point to a statute somewhere supporting your claim?