The basic SEO rule of thumb is keep Google happy. There are myriad reasons the internet giant will penalize a site within the SERPs. The terms are dictated and webmasters and SEO Companies alike are obliged to comply or risk having a domain completely removed from Google. The process is becoming more sophisticated as Google constantly updates their algorithm to punish new spam techniques. This means that specific problems rather than the domain itself should be penalised.
As an SEO agency it is fundamentally important that you keep up to date with Google’s changing algorithms in order to avoid being condemned for bad practice.