A lot of microblogging/social network is "stuff people don't want to pay to host". Some of the rest is "stuff people would pay to host, but for reasons they want to post it on services that don't allow them to pay to host". With a P2P system, you at least have the option to pay to host (=setup a server or pay a service to help serve content that's important to you around)

Honestly I was thinking more the darker side of the internet. Combine uncensorable with a hint of anonymity and you're on the hook for distributing a lot more than you signed up for.

Less cryptic - copyright violations at best, things like child porn on the worse end of the scale

Not being sarcastic there, his comment summed it up so well. Why downvotes?