Twitter (NYSE:TWTR) held its first analyst day on Wednesday, and gave us a few insights into its business. Most exciting for Twitter nerds like me was the announcement that there are over 500 million unique visitors each month who don't log into the service.

Why is this so exciting? That's exactly the question fellow Fool Tim Brugger asked in this article. Tim believes those 500 million unique visitors showcase a failure on Twitter's part to create a product compelling enough to get them to sign up and log in.

But I'm in the camp that sees those 500 million visitors as a huge opportunity for the company -- one CFO Anthony Noto believes could be worth up to $1.3 billion in annual revenue. That's without even getting them to sign up!

Twitter divides its audience into three segments. Logged-out users could be worth $1.3 billion annually. Source: Twitter

How to advertise to visitors
While Twitter doesn't have as much information about those 500 million unique visitors, it's not completely clueless about how to advertise to them. Twitter can take a page from Google's (NASDAQ:GOOG) (NASDAQ:GOOGL) book, and use context to display advertisements to visitors.

To that end, Twitter already knows a lot about these logged-out visitors. It knows what page they came from -- search engine, news website, celebrity fan page, private sharing -- and it knows the content those visitors are viewing on its own website.

The easiest pages for Twitter to monetize are its search results pages, which see 75 million unique visitors per month. Search is easily monetized because it comes with the most context. Search terms show intent, and advertisers can target users with search terms just like they do on Google or any other search engine. In fact, Twitter says it already uses search context to target advertisement for logged-in users.

With that in mind, Twitter is doing a couple things to improve search result page views. First, it gave search engines access to index its top 50,000 hashtag searches every day, allowing Twitter to show up in general Web search results. Second, it is producing curated timelines based on specific hashtags like it did for the World Cup and the NFL. The company sees thousands of opportunities to make these event timelines in the future.

The company also sees those 500 million logged-out visitors navigate directly to profile pages (200 million unique visitors), individual tweet pages (125 million visitors) and the home page (125 million visitors). There are similar advertising opportunities on profile pages, especially those of brands and celebrities, but individual tweet pages and home pages are harder -- if not impossible -- to monetize. The goal with those should be to engage visitors better.

The opportunity to engage these users better
Twitter doesn't need to convert visitors to any of these pages into users. Of course, it would love to do that, but there's an opportunity to drive engagement without getting them to sign up. The philosophy is that if users see all Twitter has to offer, they'll be more likely to sign up. In the meantime, though, more engagement means more opportunities to advertise.

Twitter plans to do this by improving profile pages, individual tweet pages, and the home page.

With profile pages, Twitter has already made several improvements over the past 12 months. It made them more media-centric, made tweets bigger and bolder, and implemented infinite scrolling. Since instituting those changes, Twitter has seen visitors viewing six times as many tweets and two times as many visitors. That's 12 times the overall engagement on profile pages, presenting a tremendous opportunity for advertisements. The company thinks it can improve upon these metrics.

With individual tweet pages, Twitter plans to use look-alike users and tweets to recommend more content to visitors. This is aimed at drawing them deeper into Twitter, and reducing the number of visitors who navigate away, which currently sits at 70% for tweet pages.

On the home page, Twitter has a tremendous opportunity to engage those 125 million visitors who never log in and just navigate away. It plans to implement its search function and present some of the most popular content on Twitter based on a user's location, which is easily scraped from a phone's GPS or IP address.

These efforts will increase the number of opportunities for Twitter to monetize its logged-out viewers based on contextual advertising.

What $1.3 billion means for investors
Noto's math to get to $1.3 billion is simple. He estimates the company can monetize users at a rate of $2.50 per year. To put that in context, Twitter currently monetizes its core users at a run rate of $5.09 annually.

In other words, Noto believes he can double the company's revenue just by implementing ads for logged-out visitors, and doing so isn't nearly as hard as it sounds. With monetization efforts for logged-out users starting as early as next year, analysts' expectation of 65% revenue growth in 2015 might be too low.

Twitter's other efforts to improve the number of users who sign up for the service, keep those who do sign up engaged, and increase its ad load make the opportunity presented by those 500 million unique visitors even greater.

To read Tim's opposing take on those 500 million logged-out visitors, click here.