blockchain.info is an online wallet and doesn't charge fee to pay hosting or what ever,all of the fee is fully given for the miners and blockchain.info don't took the bitcoin even a little bit,maybe you're talking about wallet which has provided by an exhanger,they'll charge fee about few cents or even less but it's for the service they offered,so no problem at all
blockchain.info is filled with advertisement but since they are not intrusive people don't feel when they are shown to them.
on the pages when you search for a transaction id there is one big ass ad on the bottom right corner.
and they don't even stop there, in the old version of the wallet (have not tried the new one) there were multiple small ads on the top right corner of the first page after login.