I have not read anything about sale of accounts. But regarding the multiple accounts In steem whitepaper you can see that this is already mentioned. 100SP whether it is distributed between 10 accounts or 1 account it will still have the same clout. So I don't think there is any issues with creating multiple accounts.

Over the time we will see more serious publishers getting on to steem. Once they create their brand and if they consider selling their whole company they might also need to transfer the steem account to the new owner. In cases like these it doesn't make sense to selling of accounts.

Looking at these scenarios I think the creators of Steem were ok with creation of multiple accounts and buying/selling of accounts.