After posting another strong quarter, albeit with a couple of hurdles to address, Facebook (NASDAQ:FB) should be flying high, right? Turns out investors weren't overly impressed, as demonstrated by Facebook's blasé stock price. Despite the solid quarter and year, Facebook's share price is down about 3% year-to-date.

And there is some method to the Facebook naysayer's madness: 2015 is going to be a year of transition. Diving headfirst into new advertising mediums, which in turn will put Facebook squarely in the sights of digital ad king Google (NASDAQ:GOOG) (NASDAQ:GOOGL), assimilating significant acquisitions, and managing expenses will all challenge CEO Mark Zuckerberg and team this year. So, what's a growth investor to do?

Opportunities abound
As it turns out, Facebook's Jan. 28 Q4 and annual earnings announcement is likely to be a microcosm of what investors can expect in the foreseeable future. Of its many revenue opportunities, utilizing video ads as a mainstream alternative for Facebook's marketing partners is at, or near, the top of the list in terms of driving future growth.

Zuckerberg has made it clear that he won't sacrifice the Facebook user experience by inundating the site with ads simply to increase sales -- and he doesn't have to. Along with Google, Facebook is perhaps the king of gathering, analyzing, and implementing user data to ensure the right ad, is shown to the right user, at the right time. The result is that Facebook is able charge industry-leading rates that marketers are more than willing to pay for, because they work.

The success of video spots is why Facebook is able to charge as much as $1 million per day, and marketers are lining up for more. This year alone, video ads are expected to total nearly $8 billion in revenue, and that will continue to climb going forward. Google's YouTube currently rules the video ad roost with about 19% of the overall market, but with Facebook going all in, the search king is going to have a fight on its hands.

For long-term investors, Facebook also boasts a host of future growth opportunities. WhatsApp, Messenger, and Instagram are all gaining monthly average users, or MAUs, at astonishing rates. WhatsApp is now over 700 million MAUs, Messenger has topped 500 million, and Instagram grew over 50% last year alone to over 300 million MAUs. As impressive as the user growth of Facebook's properties has been, the beauty for investors is that none of them have been monetized to any extent. In other words, Facebook is sitting on several relative goldmines that have yet to be mined.

As always, there are challenges
For short-sighted investors, which are likely responsible for Facebook's relatively ho-hum stock price performance so far in 2015, skyrocketing expenses are a concern -- and to some extent, they're right. Last quarter alone, Facebook's overhead jumped to $2.72 billion, up 87% compared to Q4 of 2013. Making matters worse, or at least giving Facebook bears more ammunition, is spending is expected to increase again this year, according to Facebook CFO Dave Wehner, between 50%-75%.

Some may also question Facebook's relatively stagnant user growth. You may recall Facebook had 1.35 billion MAUs at the end of 2014's Q3, and that total only rose to 1.39 billion by year's end. However, there are a couple of factors to consider regarding Facebook's MAUs. One, user growth is still skyrocketing, but on Facebook-owned properties, as opposed to saturated main site. Also, with significant portions of the globe still without Internet connectivity, Facebook's biggest hurdle is getting the billions without Internet online.

To Facebook's credit, even as its total MAUs are inching up, engagement levels as measured by Daily Average Users, or DAUs, are climbing by leaps and bounds. Of its total monthly users, a whopping 890 million access Facebook every day.

There are few stocks that offer so many opportunities for future growth as Facebook. And for long-term growth investors, what makes Facebook even more attractive is knowing it hasn't even scratched the surface of many of those opportunities. Near-term? Yes, spending will raise the flags of investors with short time horizons, which is just fine, because that's why Facebook is such a great value.