There are a few ifs here, but with several vaults (and my understanding of the system which may be flawed) I believe this could be pulled off.
*Gets on safe are free.
*Gets generate a potential income for the first to respond with the correct data
*chunks are put in cache once received
*Users can see what chunks they hold
*chunks are vulnerable to plain text attack (talking public data)
*chunks are requested from the closest data managers in xor space
It seems that one could compile a list of all known data that they hold (by scraping public data, converting to chunks, comparing to what they hold in their vaults) and requesting that data from different places all around the world. (thinking cheap droplet servers/botnets) if they also have vaults stashed all over the globe, and a list of the chunks each holds it seems they could generate a nice profit for themselves limited only by their bandwidth. If there are only 4 copies of each chunk, you have a 1 in 4 chance (plus cache) of getting your own.
You could also to the same by having a large private data store of data and doing the request as soon as cache has been replaced (depending on how fast data moves, maybe once a day?) so you would always have a 1 in 4 chance of generating income/playing the safecoin generating loto, assuming you know you have at least 1 chunk of your own data on a vault you control. If not, back to obscure public data. (less likely to be cached)