FranticFish - 6:28 pm on May 5, 2010 (gmt 0)
Exactly. However if that footer is in your site from the start Google seems to think it's just 'in with the bricks' - at least it used to. I think this relates to the 'over-tweaking' penalty that was also discussed here extensively a few years ago where people reported that things like changing title tags too much caused ranking demotions.
You mention 'flags' - what I took from this and other cases of 'overdoing' it is that there are actions that raise flags. One flag by itself might not be enough to cause a problem, but if more flags are raised... and maybe some 'offences' are deemed worse than others and raise bigger flags. Once you cross a certain line then you get hit. I'd imagine that the threshold varies from niche to niche and even term to term too.
And finally, it all seems to be related to trust, so what might kill one site could actually help another depending on the quality of their links.