Facebook is reportedly planning an IPO that could ask the market to value the company at a whopping $100bn. But are the social network’s better days behind it?

That’s what some are suggesting following a report by Inside Facebook, which says the company’s traffic has dropped in two of its largest and most important countries, the United States and Canada.

Needless to say, Facebook is still one of the internet’s most popular sites, and that’s not changing any time soon. For marketers, it will clearly continue to attract a significant amount of attention and investment.

But Facebook is no spring chicken, and its days of staggering growth will not last forever. The possibility that the company has already plateaued, or is in slight decline, in the markets that it first entered, would seem real.

The question for marketers: what does this mean?

In the immediate term, nothing. Even if Facebook stops growing in key markets, like the United States, marketers still have ample opportunity to increase the profiles of their presences and campaigns on Facebook.

Obviously, few marketers, if any, can claim that they’ve fully exploited the opportunities that exist on Facebook.

In fact, the majority haven’t yet tapped the surface, so even if Facebook didn’t acquire another user in the affected countries, marketers would still have one of the most sizable audiences on the internet to court for years to come barring a mass exodus that seems unlikely.

In the long term, however, signs that Facebook’s highest growth days are behind it in important mature markets should serve as a reminder that it isn’t the only game in town.

Not only will the marketing landscape on the site become more competitive as growth slows and the network becomes more mature, markets will need to face a new reality: some individuals will leave Facebook.

Here, Facebook may speed the process as it starts looking less and less like a cool place to hang out and more and more like a creepy institution from a George Orwell novel.

Up until now, Facebook’s rapid growth has masked the fact that some of the company’s users have decided to kick it to the curb. Yes, this number is small thus far, but attrition will eventually become more noticeable.

For marketers, the implication is clear: if you’re focusing most or all of your social media investment on Facebook, you won’t be able to say you have the channel ‘covered‘ in the coming years.