I've found a competitors' site that has very poor on-site SEO but has hundreds of backlinking domains (all same Class-C IPs) just because the owner has created hundreds of single-page domains with just a 200 word article on each but linking back to his main site. The spam domains are all keyword heavy and the links have keyword anchors. This sounds like it would be a lot of effort and quite expensive but just how effective do you think it would be? He ranks top 5 for lots of competitive keywords...
I wouldn't think that it is really that good. There is a decent chance that he will drop in rankings for some of those keywords as Google sorts out where his site should be. If it holds up for a couple months may be a very viable method then.
Well it's definitely NOT good, it will help you a little in the starting but then drop all the ranking down to zero or even can banned all those websites which were included in doing such thing.
He's def not been banned and his site is over 10 years old and still very strongly ranking. Seems it might work?