Twitter and the LC

Library of Congress acquires entire Twitter Archive.  Slate runs an article explaining why historians are so interested.  We have entered a blackhole when it comes to personal communications.  But what about other forms of communication- Facebook, etc.?  Twitter is not heavily used by younger people- why Tweet when you have a Wall!  While Twitter may be the fastest growing Social Media it is telling that the heaviest demographic of Twitter visitors is 35-49 years old (According to NielsonWire).