The short answer: Nothing. Yet.

That’s because the darn things aren’t even rolling out to all users for a while (see Facebook’s formal announcement last week).

But, that time will come eventually. And when it does, there will be substantial implications for marketers and brands.

For now, it’s mostly a user experience issue. Users can now search Facebook more easily (combined with Graph Search, Facebook is making strides here). And, obviously, this move makes content discovery much more easy on Facebook.

But, a few months from now, when more (or all) users have the ability to use hash tags on Facebook, what will the rub be for marketers? Here’s a few things that come to mind:

Easier to track “campaign” conversations on Facebook

You know those campaign hash tags brands use on Facebook? The ones they listed on all those Super Bowl ads this year? Well, those will actually be useful on Facebook once the hash tags are rolled out. Obviously, the volume won’t be as great on Facebook for most brands (far more tweets than their are status updates), but this should help brands looking to more accurately track conversations around campaigns down the road (especially those without access to paid monitoring tools).

Your Twitter chat potential just expanded

Brands that either sponsor or organize Twitter chats will be able to open up a whole new door to Facebook–again, arguably a more engaged (and larger) community. Of course, brands can do this now with tools like Shoutlet, but again, many brands don’t have access to paid tools like that. With hash tags, brands that participate or organize Twitter chats will now be able to have those same chats on Facebook. Of course, coordinating that might be a bit of a bear, but I’m sure a too will emerge to fit the need.

You will be able to pay to trend. Eventually.

Trending topics/hash tags will most likely be coming to a Facebook page near you soon. They’re not there yet, obviously, but I’m sure it’ll happen. Trending topics on Twitter are so popular–and it’s another great way for Facebook to enable content discovery. And, when they do institute trending topics, you most likely will have the opportunity to pay to be included (just like on Twitter). Whatever they can monetize, they probably will.

Once they enable mobile usage, possibilities expand

The curious thing: Facebook didn’t enable mobile usage of hash tags at the outset of the launch. That’s funny, because as we all know mobile phone usage is exploding. And capturing real-time conversations largely means capturing conversations on the go–not just in front of the TV (which is what Facebook is most likely after here). But those mobile conversations are key for brands. Customers at events. Customers near their stores shopping. Customers IN their stores shopping. With hash tags, they’ll all be easier to track–and respond to (again, provided customers actually use the hash tag, which as we know is a big leap).

What do you think? What are the major brand implications (eventually) for marketers with hash tags on Facebook?