I wonder how often Googlers get asked about who they should hire as an SEO consultant or firm? I get the question all the time and in fact, people ask to hire me all the time. It was interesting to see how Gary Illyes from Google responded, saying it would be a "conflict of interest" for him, in his position working at Google, to recommend specific SEOs for you all to hire.
He said on Twitter "unfortunately I'm not in position to recommend an SEO company officially, because I work on Google Search & it would be conflict of interest most likely." He then interestingly enough suggests to the person to review his followers on Twitter, saying "but if you look at who I follow, you can likely get some ideas on who to listen to."
Is Gary's follower list a good suggested SEO company directory? He is not directly saying that but he does follow some really savvy and smart SEOs.
Google did product a video and content around how to hire an SEO a couple years ago. Here is that video:
I suspect if they took the time to put this video together that they do get the question often enough.
Forum discussion at Twitter.