50 years from now, when historians are looking back at archived tweets from the billions of people of the past decades and on (being optimistic that twitter will be still around) they are going to think “Wait, what did I just read?” I believe all tweets are helpful to someone, even the tweet about the unsuccessful sandwich. As for historians, it will help them classify, suggest, and even prove that this generation is too much involved with electronics. Hey, even President Obama tweets! Then, historians can compare times between the 19th century and now, where news travels faster than before you even finish reading this post. Oh wait, news just came out.. and now.. and now.
Back to my point, any bit of information that happens in the world can be used for anything. As for twitter, we will never actually get the point of posting your failed sandwiches, but to a historian, they will go a bit further. They might actually discover something really important from a person that responded.