Facebook is about to cross one billion users.

Employees are already throwing that magic number around the office, but they're surely rounding up. The last official figure Facebook gave is 955 million users.

Based on its rate of growth, Facebook should be hitting the 1 billion mark any day now—right in line with projections made earlier this year.

That's amazing news, but it comes with a conundrum,

Right now, touting how many users it has seems like a tone-deaf move for Facebook. It risks calling attention to:

Poor monetization of mobile users. More and more of its users access Facebook on mobile, and while it's making big strides, it still makes far less money on mobile than it does on the desktop.

Poor monetization, period. Facebook makes much less money per user than Google, LinkedIn, and even AOL.

The downside of being global. Facebook has saturated the developed world. In the countries where it's adding most of its users, the population is less attractive economically to advertisers.

The number of fake users. If Facebook claims to have 1 billion users, the question will inevitably come up: Are they real?

So what should Mark Zuckerberg do?

Here's our advice: Basically, ignore the 1-billion-user milestone. Just let it pass without a big fuss.

Instead, Facebook's CEO should stick to the playbook he's followed since the site's earliest days, when it raced from college campus to college campus in a massive land grab that gave it a lock on the college market.

The message: Facebook is happy to serve 1 billion people today, but it's focused on the next billion users.

This will not comfort Wall Street, which wants to see Facebook management focused on maximizing the revenues it gets from each user now.

But Zuckerberg has already made it clear he doesn't care what Wall Street thinks. He disclosed that opinion in the company's IPO prospectus. Investors should get the message by now.

If he's going to make the company far more valuable than it is today, Facebook needs to lock in that next billion users.

Yes, they will be poorer than Facebook's first billion users. Right now. But the growth of the global middle class is an unstoppable trend. They will graduate over time from feature phones to smartphones to tablets, giving advertisers better platforms to reach them. The long-term threat to Facebook is that Google or some startup figures out how to help them connect with friends and find interesting things to read and buy better than Facebook can.

Bottom line: One billion users isn't cool. You know what's cool? Two billion.