To build — and keep — an audience, digital marketing is a must. But investing too heavily in a single platform can cost you money, customers and plenty of opportunity.

Q: When looking at our marketing spend, what’s more important for digital growth: SEO or social media?
— Chris G., Minnesota

Before consulting, I made my living as an editor in media. Each job I held taught me the same lesson: Digital growth is not about manipulating tools like search engine optimization (SEO) and social media. It’s about using them to reach customers. Then it’s your job to create a sustainable relationship off of those platforms.

I’ll give you two examples of how those tools can go wrong. My first big job was fitness editor at a men’s magazine. Facebook was relatively new, and we aggressively built our following. The result was lots of “likes” but little direct revenue we could track. That audience eventually drove significant traffic to the website — and that was traffic we could monetize. After I left, Facebook changed its algorithm, and posts drove only a small fraction of the clicks they once did. Traffic shrank. So did revenue.

My next gig was as at a health website that had mastered SEO. Higher search results led to more traffic, which led to higher advertising revenue. Then came the infamous Google “Panda update,” a change to its algorithm that penalized content trying to game SEO by using hacks like keyword stuffing. Those changes sent us into a tailspin. We had to review the site’s 500,000-plus articles, remove more than 150,000, and reinvent the editorial approach. It took 18 months to fully recover.

Chris, I don’t share these stories to suggest that social media and SEO aren’t important. They are. But dependency on any platform you can’t control is dangerous.

I like to look at businesses in pieces, so let’s consider your marketing needs. What is going to help customer acquisition and retention? What is the cost and ROI? SEO and social media are effective components of an acquisition strategy, and social media can also help with retention. Rather than thinking about which is better, think about how you can use each to support your core business.

For SEO, how are people discovering you? What questions would they ask Google that could lead them to you? Let’s say you own a car dealership and want to own “best car dealership in Minnesota.” Yes, you could go to Google Adwords and spend money on a search term. But buying your way into SEO popularity can be expensive. (And most consumers ignore obvious ads.)

Instead, consider what questions potential customers may have about, say, a specific car you sell. Win traffic by answering those questions on your site. We’ve seen clients earn hundreds of thousands of dollars of free search engine marketing by creating and owning valuable content. Google wants to reward that value, so if you build something that actually helps the end user, you will — over time — climb the ranks on the search engine’s results pages. And it will be more than worth what it cost to create that content.

Social media, on the other hand, is driven by engagement. You need to have an emotional pulse on what people care about — enough to make them spread your brand’s message. Likes, shares and comments are the by-products of an ongoing conversation. Those virtual interactions can result in real-life customers and help keep them.

The bottom line, Chris, is that no one tool will help you thrive. Google and Facebook can help. Email lists, apps and member communities can, too — and they’re even better, because you control them in a way you’ll never control giant platforms. But any great business must build an ecosystem that routinely engages its customers — and that should be your main focus.