There are several theories for why voters in California rejected a measure to legalize marijuana this week. One argument is that proponents of Proposition 19 didn’t spend enough money on the effort—thanks to Meg Whitman saturating every channel with $100 million in ads for her gubernatorial run, the $4 million spent on the Prop. 19 campaign was too piddling to register. Turnout was also a problem; exit polls show that young people generally supported the initiative, but, as in the rest of the country, they didn’t show up at the polls. (Maybe they were lighting up to celebrate the Giants’ World Series win?) Finally, there’s the bureaucracy theory—as the Los Angeles Times editorialized, Prop. 19 was a terribly flawed initiative, allowing every city and county in the state to set up its own local entity for taxing and regulating marijuana. In an anti-government year, perhaps even potheads couldn’t smoke that schwag.

All these theories have something in common—they suggest that Californians really do want to legalize marijuana, just not right now. Some day—when proponents of legalization craft a better measure and put on a better campaign, and when young people make up a greater share of the electorate—pot will become legal in California, advocates say.

I suspect, though, that there’s another reason that the Golden State electorate didn’t bother to legalize pot: Marijuana is essentially legal in California already. In 1996, voters passed Proposition 215, making California one of the first states to legalize marijuana for medical use. “Medical use” is defined with comical broadness. Virtually anybody who wants legal pot in California can visit a friendly doctor, complain of “chronic pain,” and walk out with a marijuana card in about an hour. Indeed, not only is legal marijuana a big business, it’s also becoming a pretty normal business, acquiring all the trappings of a mature industry. There are wholesalers, retailers, chains, brands, logos, coupons, and even TV ads. In September, the Fox affiliate in Sacramento began running the country’s first spot for a marijuana dispensary; in an ad that resembles every late-night spot for acne cures and diet supplements, patients of CannaCare regale the healing powers of marijuana.

But the best way to witness the retailing of marijuana is to visit WeedMaps, a two-year-old Web site that has become the primary online portal for the legal pot business in California. WeedMaps is often described as the Yelp for marijuana, but that undersells it. It’s more like Yelp, MenuPages, Craigslist, Groupon, Bloomberg, and the New York Times Dining section for pot. WeedMaps is the first place you’ll visit after getting your marijuana card—type in your address to find the best local dispensaries—and the place you’ll keep coming back to every time you’re looking for a new high. As a result, it’s become an amazingly profitable business. According to Justin Hartfield, WeedMaps’$2 26-year-old founder and CEO, the site makes $400,000 a month, and revenues are growing fast.

Like Yelp, WeedMaps offers loads of customer reviews. These write-ups cover everything you’d care to know about a marijuana shop: quality, price, selection, customer service, atmosphere, and the general safety and scamminess of the place. (Reviewers aren’t sticklers for the rules of grammar and punctuation, but they’re generally quite helpful.) There’s also a frequently updated menu of what’s available at each dispensary. For instance, I discovered that the top dispensary in my neighborhood, the Palliative Health Care Center, offers several dozen different cannabis strains and pot-infused products, including bath salt, soap (scented and unscented), soda, and a much better selection of cheesecakes than you’d find at your local chain restaurant. (I’m itching to try the Lemon Dank Cheesecake.) Plus, WeedMaps will text you discounts from places around town, features classifieds for a range of pot-related products, and offers many artfully produced video reviews of new strains. (“Wow, you don’t need much of that to heavily medicate toward the end of the night!” raves one satisfied consumer.) And the site, which now employs more than 10 fulltime staffers, keeps adding more features. Soon, it will branch out into listings of headshops and cannabis paraphernalia.

Hartfield came up with the idea for WeedMaps a couple of years ago, when he got a marijuana patient card and visited a dispensary for the first time. (He declined to tell me the nature of his ailment.) “Before that I was buying weed off a dealer on the street—like everybody else in the world, except for people that are fortunate enough to live in Amsterdam,” he said. “So when I went to a dispensary, I was awestruck. It was an amazing experience. Being able to go into a safe, comfortable location and purchase high-quality medication for a reasonable amount of money was transformative—I realized that this was the future of this industry. It was just like it was supposed to be.”

In other words, what stuck out to Hartfield about buying pot from a dispensary was how ordinary and straightforward the process was—it was just like every other retail experience he’d ever had. But of course, modern retail transactions don’t occur only in physical stores; today, we all review products and stores online before we decide to go anywhere in real life. When Hartfield went online looking for other dispensaries, he couldn’t find a good resource. This was a clear void in the industry; the market for marijuana, he saw, was crying out for information. Before WeedMaps, patients didn’t know which strains were good, where you could get them, and how much they should cost. Dispensaries, meanwhile, had no way to know what patients wanted, what they could get away with charging, and how to market themselves. And if shoppers couldn’t find what they wanted and retailers didn’t know what to stock, how would growers know what to produce?

Hartfield set up WeedMaps to cater to every player in this industry. It’s precisely because WeedMaps serves as the central information broker in the multibillion-dollar market for pot that it has a chance to make a lot of money. At the moment, most of the site’s revenues come from fees that dispensaries pay to add features to their listings. Rates start at $295 per month and go up to more than $1,000, depending on the features and level of promotion that dispensaries want. (WeedMaps, like Yelp, says that user reviews and rankings aren’t affected by sponsorships.)

The site’s revolutionary potential, however, lies in a feature called Strain Exchange. Launched a few weeks ago, the exchange is a stock-market-like listing of the most-popular strains (and their average prices) currently available at dispensaries. For the first time, sellers can see what patients want in real-time, and patients can see how much they should be paying for a particular strain. The Strain Exchange thus promises to improve quality, drive down prices, and expand markets for producers who offer the best stuff. In other words, WeedMaps seems likely to do for the pot market exactly what Yelp, Amazon, Craigslist, and countless other dot-coms have managed to do for the rest of the economy.

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