I have been recently having a look through Bitmessage and would like to gain a greater understanding about why certain choices, e.g. Streams,  were made etc.

So this is my understanding of the use of Streams & POW in Bitmessage. Please correct me if I am wrong...

[POW]

Proof of work acts as a limiter on the ability of someone to post a message over a broadcast channel.

• It serves to deter SPAM.
• By making it more expensive to send a message, it acts as a way to reduce the number of messages sent over a channel, reducing the bandwidth+storage costs of each node.

The POW difficulty need not be static but could adapt dynamically in an effort to constrain the bandwidth + storage requirements of each node to some fixed level

• One could have different POW requirements for each channel

[STREAMS]

If there were no Streams, we would be left with a best-effort broadcast channel.

• This would force each node to be responsible for the relaying and storage of a huge number of messages.
• Or the POW difficulty would be so high as to render the system useless
• It would not scale.

So we partition the network into a number of Streams, where each Stream is a best-effort broadcast channel.

• Each identity is assigned to one stream (it is fixed in the BM address).
• Some streams may be more active than others, node requirements(bandwidth/storage) will vary.

Partitioning is an effort to even out the network load.

• The only opportunity to do this load balancing and create a new partition is when a user wants to create an identity (BM address)
• If the current stream is deemed 'too busy', the identity will be created on a brand new stream

Once a stream is established, there is nothing the network can do to make itself more efficient and more evenly distribute the load on the nodes.

• It must resort to making it more difficult to post messages, by increasing POW difficulty
• This will likely not be in the user's interest

At my current level of understanding, it seems to me that Streams are quite a rigid mechanism. I see two problems:

• Once a stream is established, it cannot be re-partitioned because each identity is directly linked to a particular stream
• There is a trade-off between cost_to_run_a_node and level of anonymity. If a stream is quiet, the node's own messages will be less well hidden than if a stream was really chatty. In the current system, the user is less empowered to make a choice based on his own individual needs.

Thoughts ...?