I'm sure this has been raised already, but surely miners are incentivised not to forward transactions with transaction fees?
This isn't a big deal at the moment, but as transaction fees become juicier per block, won't miners (and in particular, big pools) try
to keep transactions with fees for inclusion in the blocks they solve rather than broadcast them to other miners ?
Transactions without fees take much longer to get included in a block. The reality is that all nodes bounce around transactions, so if a miner kept a transaction secret, someone else would pass it around.