Note Steemit is accumulating numerous copyright violations. I've read it is $150 per infraction in potential liability.
From what I understand, all videos and pictures are linked externally. At the blockchain level there is only a url link - which may respond now but not after 3 years.
Copying text could be another issue though.
The amount of articles reposted without citations is pretty ridiculous.
Even if it is linked externally, Steemit serving the links could be liable for using copyrighted content in their business. Although it is on the Steem blockchain, Steemit doesn't have to serve the (embedded links to the) content. They should implement a copyright compliance team. Steemit is a centralized entity and thus is liable.
That is unless the user is downloading a client and the user is deciding which content from the blockchain the user wishes to request and view.