Learn About FreeNet Straight From The Source
It's fairly trivial for Spam Inc. to deal with decay - they can simply put their 2000 Mb of garbage into Freenet, and then request various bits of it repeatedly. If they're smart, they'll request it from different Freenet nodes each time, ensuring that the data appears to be in higher demand. They just need to make sure that they use keywords that people are likely to guess. If we're lucky, the spammers will be competing with the warez/pr0n folks for their keywords....
Information wants to be free