Bootstrapping a p2p service like this is extremely hard, so any way an existing network can be leveraged is ideal. I want distributed storage, and if I can exploit the bitcoin network for that purpose, I will do it; distributed systems aren't based on the assumption that everyone is "nice".
As mentioned, you cannot stop this usage, only change the price. I personally would love to have a, say, 1KB filesystem
that I know is being backed up all over the world and people have an incredible financial incentive to hold onto, and I would be willing to pay quite a bit for it. Many others would too.
I just found out about bitcoin a couple of days ago but I will build such a "bitcoin block store" as a proof-of-concept, using whatever I can. It will support a very modular encoding scheme to encode the data blocks in transactions, with the encoding becoming more and more steganographic as needed to counter any attempts to stop me.
There are much better ways of achieving distributed storage than bitcoin. There are, however, specific data that can idealy be stored in a proof-of-work system like bitcoin. For example, DNS. However, for the vast majority of distributed storage, please use google.
Infact, thinking further, I think this is actually the correct/arbitrage-free way to price bitcoin transactions(by storage).
It's already clear that the correct/abitrage-free price of a bitcoin should be the expected cost of minting a new coin using say, amazon EC2 (i.e., a bitcoin value is pegged to the value of cpu time). I am now pointing out the correct/arbitrage-free price of a bitcoin *transaction* is the expected cost of storing the same amount of data in a similar widely replicated system (i.e., the transaction price is pegged to the value of distributed storage).
That is a common misconception. The price of bitcoin is loosely related to the cost of generating them, but that is in no way the only factor and currently, the price is far away from the cost most miners pay to generate them.