Is is possible make the site drop in SERPS or be banned completely from google? My client thinks that that's what's happening now to two of his sites. He reckons his rivals can do that
You can, by blasting the hell out of a site for 3 days straight and then just STOPPING. The best way to prevent that is provide steady link building every week ti circumvent the bad links being sent to your clients site.
Google "Negative SEO". Lots of controversy on this topic but yes, it's possible - at least in theory.
Yeah I can see where this is possible. Maybe if you just poke Panda and Penguin with some bad backlinks ect. RedClover
Normally it's only temporary though. And there are some well documented ways to recover and make it harder for it too happen again. Steady linking to all important URL's in your site is important. Scritty