Post Penguin SEO for Small Businesses?

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I'm trying to rack my head around how a small local business like say a hairdresser or dentist will have SEO in the post Penguin environment. I mean, how relevant will content marketing going to be for your local dentist? I keep on hearing that after Penguin you have to have killer content that everyone what's to share with everyone else to rank in SERPs. But I mean, what's "killer content" for a local dentist and who goes around sharing their local dentist's content anyway? How much social media engagement for a local dentist should you actually expect? Let's say I'm going to get a root-canal, the last thing I can imagine myself doing is going on the dentists blog and liking or sharing their content.

It just doesn't seem realistic for small local businesses or am I missing something?