According to a blog post by Gayle Osterberg of the Library of Congress, the program will maintain the archive of tweets from 2006 - 2010, and will continue to acquire tweets on a selective basis. A white paper on the change says that, in general, tweets archived will be "thematic and event-based, including events such as elections, of themes of ongoing national interest, e.g. public policy."
The white paper also points out that the volume of tweets has increased dramatically over time since 2010, and that its text-only archives miss important visual information of recent tweets. The Library feels that the first 12 years of tweets represent the rise of an important social media, and that the full-text collection can now be limited. "The Library generally does not collect comprehensively," says the white paper. "Given the unknown direction of social media when the gift was first planned, the Library made an exception for public tweets. With social media now established, the Library is bringing its collecting practice more in line with its collection policies."