Oh, I'm not necessarily talking about techniques. I'm just wondering where immunity starts. I mean, my site is tending towards immunity (we can get away with stuff we definately could not 5 years ago). I've seen verticals that are oligopolies wrt SERPS that appear to be engaged in link warfare. No Slap.
Then again, I've seen year-old sites that are shooting up the SERPs, hitting page 1 on multiple converting terms, beginning to be players. These new sites begin to experiment with behaviour they see all around them, only to get The Slap.
I've seen members here who used to warn strongly against paid links become a convert across the last couple of years. Others who have preached against the orthodoxy (often a bit vocally) have been marginalised. I think now there is a general awareness that paid links work, but there is clearly a line- and that line seems to shift, not with just with algo changes, but with site maturity.
I think a good discussion about tolerances is in order- with a bit more finesse than the blanket "Paid links are bad, m'kay" or "everyone does it, jump right in" which appears to be dished out with reckless abandon.