[rickycook]

from what i understand, you get a reward for serving the data, so you miss out on a good portion of bounty. you probably COULD attack the data like that, but it would cost you which might stop large scale attacks

*EDIT: and not just for serving it, but for serving it quickly.

from their site:

> Are you in the middle of a dense city? Do you have access to very fast Internet pipes? Have a rack in a carrier hotel? Perfect! In Filecoin's Retrieval Market, miners get rewarded for delivering content quickly. This makes the retrieval market good for miners who have low-latency, high-bandwidth connections to lots of users (but not necessarily the most disk space).