Coming up any day now, there’s going to be one helluva party at Facebook. Champagne, confetti, speechifying, really loud music — you name the hoopla. And why not? Companies don’t go public for a gazillion dollars very often.

So party on, Facebook.

Just beware the day after. Actually, beware the year after and the year after that.

Because once Facebook has its massive new liquidity infusion, the company stands to get nailed by something that can hurt a lot more, and last a lot longer, than a hangover: a changed culture. That is, a culture of diminished urgency, of game-over-we-won, of not-invented-here conceit.

Now, it practically goes without saying that such cultures can (and too often do) crop up at all sorts of companies for all sorts of reasons. But most often, arrogant or otherwise indolent cultures tend to track with colossal market success, and they definitely tend to be exacerbated when a whole slew of employees are suddenly billionaires and millionaires. It’s just plain hard to generate wide-scale paranoia, passion and humility — the defining values of an energized enterprise — when everyone’s feeling fat and happy.

And after the party, Facebook is going to be feeling pretty darn fat and happy, especially the people who’ve been around the longest and control the most action — its senior managers.