It was another blow-out quarter for Facebook (FB - Get Report) , as the stock has hit an all-time high and surpassed $300 billion in market cap.

The number of people using the service every month, not to mention daily, are showing incredible strength and getting stronger. There are now more than 1 billion daily active users -- it's remarkable.

CEO Mark Zuckerberg and his team made sure that the core Facebook product of Newsfeed and Messenger kept drawing in users and monetizing like crazy, especially in mobile, where it now gets more than three quarters of its advertising revenue.

Facebook hasn't done everything right, but they've done the big things right. All the credit goes to Zuckerberg and the team there, as they had the foresight to acquire other services like Instagram, WhatsApp and Oculus.

Everyone is gushing about them today, but is everything really so rosy?

Here are the biggest opportunities and limits for the Menlo Park, Calif.-based tech giant:

Opportunities:
  • Instagram: Although Facebook has started to ramp up its monetization of Instagram, it's clear they are still at the beginning stages of this. Additionally, Instagram just gets more and more popular - especially here at home. It's now at over 400 million users and keeps growing.
  • Digital Ad Spend: Believe it or not, Facebook is still at the beginning stages of vacuuming up digital ad spend money. There was a stat in an article in The Wall Street Journal showing a survey from RBC Capital Markets that 61% of marketers planned to spend more money on Facebook next year. If you're going to spend money on mobile, where are you going to go first?
  • Video: Video ads have really started to roll out in a big way this year for Facebook. So, this type of ad spend has to go up along with its pricing.
  • WhatsApp: Besides Oculus, this is Facebook's biggest bet that they're currently not doing anything with. They're letting it grow to past a billion users. When that happens, watch for them to start monetizing it as they've started to do with Messenger.
  • Messenger: I've been extremely impressed how aggressive Facebook has been in beefing up Messenger in the past couple of years - especially after they dropped nearly $20 billion on WhatsApp. They are now in the early stages of trying to mirror a WeChat-type strategy for Messenger so that you can conduct a lot of commerce within.
  • Commerce: Beyond Messenger, Facebook wants to extend commerce to its main app.
  • More targeted ads that monetize even better: Part of Facebook's secret sauce is their ad tech. It's already good but it can likely even get better in the next few years with more targeted ads that they can monetize at even higher rates. Watch for that.

Limits:

  • Users: Facebook literally has a "first world problem:" it's running out of developed world users. This is why it is pushing its Internet.org initiative so hard. To keep user growth up, it's got to go gang-busters into areas like Africa, India and potentially China.
    Facebook's year-over-year user growth rates continue to flatten. They won't be flattening out at like Twitter (TWTR - Get Report) has done, but as it continues to approach flat-line, analysts will naturally start gnashing their teeth more about it.

  • Mobile Ads as a % of revenue: This latest quarter saw it hit a new all-time high at 78% or slightly more than $3.5 billion in revenue. That's great. What's not great is that if you follow this metric's trend over the past few years , its trajectory is getting close to flat. Have they hit the upper limit of mobile growth? The answer of course is to ramp up the elements described above in the opportunity section but it still should be cause for concern.

  • RSI: This is purely a short-term worry but, as of this morning, Facebook's Relative Strength Index (RSI), or how strong the stock has been recently, is around 75. The last time it was so high was last July before the global economy worries took the stock down to $80.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.