CainIV - 7:03 pm on Apr 3, 2012 (gmt 0)
Fathom - I am not jumping to causation from possibility.
I am also not doubting your experiences.
But it only takes one instance of a false positive to render any supposition not true for all. Which seems to be the case here.
Certainly there are examples where Google has seemingly completely discounted links. And there appears to examples where Google has NOT discounted links that were NOT put in place by the client or marketing company.
Again, whether or not those were done by a competitor is moot point. They were built by someone. And the suggestion that they could hurt rankings then leads to the point that obviously a competitor could have done it (or could replicate those results if careful by doing the same thing)