Facebook is still trading well below its IPO price, and suddenly it’s hip to dump on the company. Sure, that IPO was ugly, and its negative effects will continue to be felt for some time. But to everyone out there who thinks Facebook has already played all its revenue tricks and so isn’t worth all the hype, I say: hold up. This thing’s a long way from over.

Even if Facebook’s platform ultimately crumbles, its news feed becomes irrelevant, or people find a better way to share photos with their friends, the social network is still the glue for nearly 1 billion people. That is, you know, kind of a big deal. As long as it “owns” those connections, Facebook could scrap everything it has built so far and still be incredibly relevant.

Actually, that’s almost what it has to do for mobile. As I have said before, and as everyone’s grandma now readily acknowledges, Facebook’s desktop experience doesn’t translate easily to mobile, which is how most people will be spending most of their Internet time in about, like, five minutes. But you have to be ass-burningly naive to think that Facebook isn’t going to do something about that.

Yesterday, I wrote that Facebook should build a mobile browser with a view to becoming the dominant HTML5 app platform. Not only would that be smart planning for the day when iOS and Android are inevitably overwhelmed by app overload, but it would also open up new revenue opportunities. And, lo and behold, today emerged a strong rumor that Facebook is looking to buy Opera.

That would be such a smart move. A total game changer. Buying Opera would give Facbeook a huge opportunity to build a new experience purely for mobile. And then we would have to reassess everything we thought we knew about the company. Because Facebook isn’t a “product.” Its news feed and photos are mere features that complement its immense network. The reason I can never “leave” Facebook is because I wouldn’t really be leaving anything. I’d actually be severing valuable ties to friends and contacts that are extremely difficult to maintain in any other way.

So the challenge now for Facebook is to make that friend network as useful to me as possible in a mobile context. Can they do that? Well, they’ve got a better chance than anyone else. And if they turn Opera Mini into a pseudo operating system that dominates a mobile future in which we have high-speed wireless connectivity all the time, then they’ll be bigger than Google.

Building the mobile future is a massive opportunity for Facebook. Android and iOS won’t dominate forever. I’ll say it again: Let the mobile browser war begin.