Hi and welcome @Skal3ton !
Nobody can stop a huge company to join the network, not even the developers itself. If the algorithms are right then this big company can’t earn all the safecoins. This is a thread where someone actually asks the same questions as you: Massive scale maidsafe farm
I hope I understand this correctly 
Only the one who uploads the information can see the information. The uploader has got the glue to match the parts, others can’t see anything about what there is stored and where it has been stored.
What do you mean with share? email and personal messages or storing it publicly ? Either way, I’m not sure if I can give you the correct answer but hopefully the other answers helped you :).