Securities feeds are, I suspect, more write-dominant and have a much lower fanout rate. They also don't have the outlier-retweeting-outlier or outlier-tweeting-@-outlier problems.
Yes, much more write-dominant. Apps which are built on top of the feeds can create issues, though. E.g., An obscure ticker pasted into a chat room with 500 people instantly starts monitoring in all their windows -- not just the static price (equiv to a RT), but the live feed. That would be as if A RT'd B and suddenly all of A's followers added B to their timeline. The degree to which that happens depends on how many features like that are integrated into the app.
I have no idea why you're getting so much pushback. Products like those offered by Bloomberg ingest and distribute massive amounts of data in real time, as well. The comparison is completely suitable.
While their products for investment managers are mostly run off of persistent databases, the trader terminals rely on a high-volume, nebulous fan out. For many traders, a five second latency is unacceptable.
Incredibly interesting talk and a good write up. Twitter continues to impress! I was surprised to see Redis playing such a critical role, too.