I don't know if we'll ever know where the line in the sand is - it's blurred... and you're 100% correct. Google does like it that way. There doesn't seem to be enough clarity for a webmaster or
SEO to know whether she/he has crossed that line. I try to follow the Google guideines but even that isn't enough based on so many of the WPW posts I've read.
After making a (truly)innocent mistake last month and getting whacked by Google that I am, in a manner of speaking, paralyzed, and afraid to try anything new.
How does one know when they're too close to the flame without waiting until they get burnt?