How do you make money as a message bus? I'm not saying I disagree (I take no position on the merits of Twitter-as-a-servce, as I am not a user), but clearly the Best Minds have decided that the attention economy (read: ads) is the way forward. How do you pay for that critical mass? Twitter isn't something that falls out of infrastructure -- decisions had and have to be taken to spend resources.

While selling people to advertisers is getting harder, and therefore less margin-friendly, it'd take a braver company than Twitter to turn their back on the model. IMO.