I think in trying to figure out an answer to your question in the title though, google needs to be tricked into thinking your site is an authority site, which requires the backlinks.... these guys have pulled that off, and I think they get some backlinks from people that don't bother to check that the site is garbage trying to upsell, and also they offer some kind of toolbar, so I don't know how that plays into the equation at all, perhaps there is something else going on in the backlink department spam wise or otherwise, but it is definitely a big part of what is going on here
really though, a site like that is the scourge of the internet,
https://www.google.com/webmasters/tools/spamreport