For a long time I have been saying that storage is cheap and that one should assume that anything put out on the Internet will live forever. It looks like that is even being institutionalized. The US Library of Congress recently announced that it will be creating a public archive of every tweet sent since the founding of Twitter. This kind of resource will keep tabloids in business for decades to come. Generations of celebrities yet undiscovered should be concerned about their old unguarded, but now professionally preserved, brain droppings.
For the record, I am not opposed to this archiving. It is happening anyway in private databases. This just makes the issue more visible and helps to raise awareness. It is similar in many ways to The Internet Archive project.