Twitter recently held its first-ever developer's conference in San Francisco, and among the highlights was the announcement of open annotations. With the ability to add any kind of metadata to tweets, we're looking at what could be the most disruptive thing to happen to our 140-character friend since, well, the beginning.

So long, Hash Tags

The way it works: Open annotations allocate Twitter an extra 512 Bytes of space (with an expected increase to 2KB in the future). Currently the metadata format is open, making it a free-for-all in the developer circle. Basically, it's a virtual can of worms.

Some of the uses we expect to see in the near future include:

Categories: This would move hashtags to annotation space. For example, there could be topical categories or info type categories for music, news, videos, etc. 

Rich Media: Images, music, video--everything gets attached. Think of the handiness of being able to embed all that junk on Facebook, now available on Twitter.  

Targeted Advertising: Metadata is able to carry advertising offers and conditional codes that determine eligibility. Adding location data (like that of Foursquare or Gowalla) would allow people to know when pizzas are $5 in their neighborhood, and so on. 

Speaking of location, ramping up Twitter's current location-based-services (LBS) is also probably on the way. Imagine traffic tweets, or all tweets about specific community locations. 

Private Sharing: Some nervy speculators have gone as far as to guess at a Twitter e-mail client, but that seems a bit heavy at this stage. Sending information privately, however, is totally feasible. 

News: A news story's location (or other such details) can now be put into the metadata of a tweeted headline. For example, a user can tweet about a volcano grounding hundreds of planes, put the words Iceland, Europe and France in the metadata, and the headline will be picked up in a cursory search. This means the 140 character limit should no longer a problem for SEO

Dessert or Disaster?

The list of possibilities goes on and on--all the way to a point of no return. What we mean here is that it's very possible that developers are going to get carried away with all of this new wiggle room. Keep in mind that if one developer adopts one kind of metadata, other applications will need to recognize it to make it useful. 

Moreover, some folks in favor of the standardization of classification systems seem a bit perturbed. "It's hard to think that creating a giant living library without consulting some librarians is a good idea," noted Marshall Kirkpatrick of ReadWriteWeb

"There has been a lot of emergent behavior around how to relate to tweets anyway, without our imposing much structure around it," argued Platform Team member Raffi Krikorian. "The Twitter platform is continuously evolving - the developers will figure it out. Twitter developers iterate in public."

Let's hope some open standards crop up so that this new development doesn't send everyone into the crazy house. Writer Raj Dash guesses -- and we suspect he is correct -- that "Twitter wants to let third-party developers come up with options, which they might later absorb into a sort of AML or Annotation Markup Language that could help the tweet search engines of tomorrow that will need to filter through all the metadata."