A good write up Dave, but do you remember the mess we had before blacklists?
Our company hosted a small server with UUNet, and at that stage we paid 30c a Mb, back in the early 2000's. Before blacklists we had in excess of R7000 of traffic we could not allocate to any one client, as the server would receive the mail, determine it's spam and chuck it. Introduce blacklists, and that amount dropped to well below R1000.
That was a smallish installation for a only a couple of clients. If that installation could benefit like that, what would the impact be on larger installations? Perhaps now that bandwidth costs have come down so much, it's not such a big money saver any more, and perhaps they commercial reason for being used might not be that relevant.
I still hate spam, and I still do everything in my power to minimize the amount of crud that lands in my inbox, and that includes using blacklists. We now use it to add a score to SpamAssassin, and not to block outright.