Pinning ensure that the content doesn't get pruned when your clear your node's cache. I think as long as you have a block of any file you'll be a provider as well.
I think this opens up an issue of copyright, there are several public IPFS Gateways available on via HTTP. If you host a bad file, you can essentially pull it through any of these public IPFS Gateways to create other seeders for your file.
Keep in mind, there is no guarantee to how long those seeders will have the file, but they do become seeders for your file for some amount of time, at least until they clear their cache or other files need the space and prune your file.
This is one reason I stopped running an IPFS Gateway. You don't have to look very hard to find copyrighted material being served via IPFS.
I think this opens up an issue of copyright, there are several public IPFS Gateways available on via HTTP. If you host a bad file, you can essentially pull it through any of these public IPFS Gateways to create other seeders for your file.
Keep in mind, there is no guarantee to how long those seeders will have the file, but they do become seeders for your file for some amount of time, at least until they clear their cache or other files need the space and prune your file.
This is one reason I stopped running an IPFS Gateway. You don't have to look very hard to find copyrighted material being served via IPFS.