Library of Congress to catalogue Tweets

Click on this link to read a Washington Post story about how the United States Library of Congress is going to archive public Tweeter messages, some of which are apparently regarded as being historic in nature.  Do you think this will change the nature of Tweeting if people know their messages may end up in the archive?  Are there concerns about confidentiality?  Or is Tweeter by its very nature a non-confidential medium?