Facebook announced yesterday that the company is rolling out hashtags--those little keywords marked by the pound sign (#) that first became popular on Twitter. It's a logical feature for the network, especially now that hashtags are used on pretty much every social site and app

In a statement, the company wrote:

Hashtags are just the first step to help people more easily discover what others are saying about a specific topic and participate in public conversations. We'll continue to roll out more features in the coming weeks and months, including trending hashtags and deeper insights, that help people discover more of the world's conversations.

From a Facebook advertising perspective, the hashtag is just another way to mine more data from Facebook users--valuable information that can be repackaged and sold to brands who target particular demographics on the site.

The only problem is that it's unclear if users really want hashtags. And it's also unclear, more generally, if users want to treat Facebook as a vehicle to "more easily discover" things. It's no secret that Facebook is slowly building up its search functionality, and may eventually compete with Google in the "search" and "discover" space. 

But by doing so, the social network runs the risk of alienating users who see Facebook's primary utility as a way to keep up with friends--not discover new things. 

Consider the evidence from last month's Pew Internet report. The researchers found that "teens show that they have waning enthusiasm for Facebook, disliking the increasing adult presence, people sharing excessively, and stressful 'drama,' but they keep using it because participation is an important part of overall teenage socializing." 

In other words, teens are unhappy because of too much stuff happening on the site--even if they have no plans to leave the social network

But next year or even next month? This notoriously fickle fan base loves to change its mind and move to the next new hot thing. And even if Facebook's growth is currently healthy--its user base grew 26 percent since last year--moving into new categories (or, let's face it, change of really any kind) could easily alienate current users. That's a path Facebook has already walked down before. 

Over the next several years, the question Facebook executives must face is this: How do you grow the business, expand sources of revenue, keep investors happy--and not completely piss off users? #Notwithhashtags.