Originally Posted by deepsand

Likewise, so did the OP here. Therefore, the proper answer turns on the issue of probability.

Were said effect easily obtained, then we should expect to see evidence of such occurring frequently enough so as to be easily observed. To hold that such effect is not observed simply because of the underlying methodology being an obscure one is untenable, as it makes the exceedingly unlikely assumption that such knowledge is possessed only by those of good will.

Therefore, while said effect is theoretically possible, it is presently quite improbable.

Originally Posted by deepsand

SEs recognize that one cannot control all IBLs, and do not therefore penalize you for such. IBLs can be positive or neutral, but not negative.

Where people get into trouble re. links is with OBLs; here you do not want to be found pointing to "bad" sites.

Originally Posted by deepsand

The obvious and logical way for a SE to handle such links is to simply fully discount them, i.e. give them zero weight. Zero weight = neutral.

There is no evidence that Google's PR algorithm assigns a negative value to any IBL.

In the loose sense of the word, one can be "penalized" by way of legitimate IBLs not being given their full due weight.

Originally Posted by deepsand

And, as I have never claimed that the effect that you champion is impossible, I am not incorrect in stating that, as a practical matter, one need not be concerned re. passively acquired IBLs from "bad" sites.

Originally Posted by crankydave

Can IBL's hurt you? The short answer is yes. I've see it happen first hand. This is why it's important to build and establish a solid link profile from the very beginning. Don't look at the individual links and don't worry about them. Remember, it's the effect of the aggregate.