Source: Twitter

Despite its slow active user growth, Twitter (NYSE:TWTR) pleased investors last month when it reported its fourth-quarter earnings. Both revenue and earnings came in well above expectations even though the platform added just 4 million net active users from the previous quarter.

Going forward, monetization will continue to hold a higher importance to investors than user growth, as analysts come to terms with the fact that Twitter will never become the mass-market product that Facebook (NASDAQ:FB) is. It's good for investors to look at both what could go right and what could go wrong for their companies. We can't predict what will happen to a stock, but let's take a look today at three reasons Twitter stock could continue to rise.

New features
At Twitter's analyst day in November, CEO Dick Costolo outlined his vision for a lot of new features for Twitter. Since then, the company has already started to deliver.

The company introduced new video capabilities to the app last month as well as improved private messaging capabilities. It also started populating new users' timelines automatically with its Instant Timeline algorithm that uses its contacts to create a timeline based on the new users' interests and their friends' interests. On top of that, it also added the "While You Were Away ..." feature that puts important tweets users missed since their last login at the top of their timelines.

It's also adding non-consumer-facing features. It's providing businesses with video-related advertising tools. It's also improving publishers' capabilities to embed tweets or use tweets in their apps.

All of these efforts are aimed at improving engagement of both existing and new users. Higher engagement, even without active user growth, will lead to more timeline views and opportunities to monetize users.

Twitter still has plenty more features it can work on. At the analyst day in November, Costolo mentioned the company wants to start producing more stand-alone apps. That's a strategy Facebook has pulled off quite successfully, and ultimately results in higher engagement rates.

Improving the logged-out experience
CFO Anthony Noto believes Twitter's logged-out visitors could be worth as much as $1.3 billion annually. To put that in perspective, Twitter generated $1.4 billion in 2014, and analysts expect the company to generate $2.38 billion in 2015.

Last month, Twitter unveiled an experimental logged-out homepage, that is aimed at providing a glimpse at the value of Twitter. Eventually that page will be optimized to show logged-out visitors advertisements. That's a vast improvement over Twitter's previous homepage, which simply asked visitors to sign up.

The new homepage is key because Twitter receives a lot of free advertising through television, website and app syndication, and a new deal with Google will put more of its content in front of logged-out visitors. Twitter needs to show people that have never used Twitter reasons to sign up.

Beyond that, it needs to monetize users that never plan to sign up. It may be awhile before we see ad units displayed to logged-out visitors, as Costolo indicated the company is focused on "a delightful user experience" first. The ongoing Cricket World Cup, and its curated timeline represents another opportunity to introduce millions to Twitter and potentially monetize them. This year, visitors won't need to log in to experience the curated timelines like last year's FIFA World Cup experiment.

Additionally, Twitter is going after the hundreds of millions of people that read Twitter content, but never visit the website. The company introduced its first partnerships with content syndicators like Flipboard to place advertising units in syndicated tweets. Adding more publishers to this program represents a massive revenue opportunity for Twitter, with hundreds of millions of more eyeballs seeing Twitter ads.

Growing ad prices
While Twitter is taking steps that may actually reduce its timeline views per user -- and is thus not going to report the metric any longer -- its average revenue per user is improving dramatically. Twitter's long-term goal is to display one ad for every 20 tweets, and it's still a long way away from that number, according to Noto.

In the near term, Twitter is focused on keeping supply under control and growing demand as much as possible. This will result in an increase in average ad prices, and it's something Facebook has pulled off extremely well over the last couple of years. Facebook's average ad price tripled last year. Last quarter, Twitter saw its first year-over-year ad price increase since going public. That trend ought to continue this year as the company improves its targeting and attracts more advertisers.

Even without increasing ad load much, improved engagement and organic user growth should fuel a significant increase in total ad revenue. With analysts expecting 70% revenue growth in 2015 and user growth slowing on a relative basis, improving ad prices will be key to beating that mark.

A strong outlook for 2015
Twitter provided guidance for 2015 in line with expectations. Note, however, that Twitter has a track record of being rather conservative with its guidance, so it shouldn't be too much of a surprise if Twitter "surprises." With new features and new revenue opportunities on top of its improving ad revenue per user due to rising ad prices, there are plenty of reasons to be excited about Twitter's potential in 2015.