You see all those xrummer blog comment links and forum links out there... but that does NOT mean that it's helping. Most likely those links are just there to hide the links that are actually helping the site rank. That's typically done in cases such as the one you're describing. If you can spot it, Google can spot it and just ignores those links.
Wow polluting the internet to protect your Golden Goose sites for backlinks.. I usually expect the worst but this wasn't on my radar. It seems very plausible however.
My understanding is that they used to damage your ranking, but then people realized that spamming links to competing sites was an easy way to improve your ranking, so Google stopped.
