It's pretty much useless now that Google actually penalises people for this - pretty funny that brands who use to do this now have to beg for their spam to be removed.
Basically they would spam these out to not look overly spammy, and have their website and name listed as their website they are trying to promote as people use to believe that having millions of shitty backlinks is good SEO.
It seems pretty counterproductive for Google to penalize the linked-to website for this, because they don't necessarily have any control over the links. This means that now a good strategy would be to make a bunch of spam links to your competitors' websites and have their rankings go down through no fault of their own. While that would be less effective than having your own go up, it's still useful.
What Google should do is make the links have no effect at all, thus preventing this abuse.
This is tricky. Generally the spammers are doing it because they're paid to do it by someone. Penalizing is the right thing to do. But you raise an interesting point - perhaps an unscrupulous firm would unleash a spambot pointing to their competition, to damage them. I'm not sure of a good way for Google to differentiate, other than your suggestion of ignoring.
Thank you for allowing me to talk myself into a circle. :-)
A lot of these guys are all about A/B split testing. If they find something that hurts rather than helps, they'll use that tactic as an offensive on their competition.
Basically they would spam these out to not look overly spammy, and have their website and name listed as their website they are trying to promote as people use to believe that having millions of shitty backlinks is good SEO.