By the way, all normal money transferring methods allow you to attach a message to the payment. Bitcoin failed to provide such capabilities as a built-in feature. It makes so much sense to encode payment details in the bitcoin transaction and it isn't even wrong. How on Earth can you call encoding payment details in bitcoin TX an abusive behaviour when ALL BANKS ALLOW THIS on their centralized ledgers. That's it. My last sentence just demolished all arguments of any opponent to encoding payment details in the BTC TXs.
BIP70 which is for payment requests, allows both the customer and the merchant to attach memos to payments, although I don't think that these memos will be stored in the blockchain. However, AFAIK those memos do stay where you really need them, in your wallet. You don't need (or want) everyone to know what you were spending your Bitcoin on, which is what encoding those memos into transactions in the blockcahin would do.
Ok that's cool, but are the memos cryptographically signed? Is it easy to verify that the text is written by the person who sent the bitcoins?