Huh? People are using Twitter to create these events? Who else would you want to process it? It's not a bottleneck to put things through Twitter if people are literally using Twitter
Yes. p2p systems would be the alternative and would, as a whole, process billions of messages but in a distributed way where each node only processes ~100.
I'm further suggesting there there is a relationship between scale and ethics, via moral hazard, that is worth exploring. Too bad I'm getting downvoted instead of engaged with.
You haven't really explored what or why the moral hazard could be, so your current comment really sounds like "twitter big, ergo twitter evil". Its sort of on you to surface your idea instead of expecting strangers to engage with you - you seem perfectly pleasant but it frequently leads to very negative interactions.