In the MAM introduction article there is for example this part about the message size:
These messages can have any size; however, a heuristic evaluation would demonstrate smaller messages yielding higher potential for data integrity. For example, one could transmit an encrypted 4k video using MAM but this will saturate the network leading to a lagging user experience.
Here I'm not concerned about the lagging user experience for a subscriber as it's obviously not a good use case for MAM but my concern is, how will the network/tangle suffer if people would still actually send such big data streams?
From my understanding data streams are 'broadcasted' to all nodes (like normal transactions) and subscribers only qualify as such as they know the address of the stream (= channel ID) and decryption key.
This would mean that only few but data intense streams could put the whole network under heavy load up to a point where full nodes on slower connections could become practically unusable. It would also mean a much faster tangle size increase between snapshots which could also become a problem for smaller full nodes (of smaller companies or individuals).
Am I missing something here or are there countermeasures?