Is it time to move data storage (of things like music, images, virus definitions) out of the block chain? This is a technical question and I don't have the answer. I would like someone to explain why this data is necessary. 

If your answer is receipts or smart contracts, then my question is, "Why not put that in side chains?" I see two problems with this data being in the bitcoin block chain: First, it allows malicious data to be inserted. Second, it takes up more block chain space. Here is the cointelegraph article about music:

http://cointelegraph.com/news/114172/music-copyrights-stored-on-the-bitcoin-blockchain-rock-band-22hertz-leads-the-way

This question is a copy of my post here:

https://www.reddit.com/r/rBitcoin/comments/355pvr/time_to_move_data_storage_of_things_like_music/
It certainly isn't "necessary" for proper functioning of the Bitcoin currency, it's just something that people noticed they could do.  But there isn't any obvious way to stop it, short of a complete overhaul of the Bitcoin protocol.  There are lots of ways to insert small pieces of arbitrary data in a Bitcoin transaction (including even the addresses themselves).  So I don't know how we would go about "moving data storage out of the block chain" even if we wanted to.  We certainly can't do anything about the data that is already there.

The current standard way to achieve this is with the OP_RETURN opcode in a transaction script.  I understand the Bitcoin developers actually took steps to make this feature easier to use: not particularly because they wanted to encourage people adding data to the block chain (as you say it takes up space), but because OP_RETURN is less disruptive than some alternative methods (for one thing, it is limited to fairly small payloads).