Will Twitter do something like this? I don't think so. But it's also a crapshoot whether your tweet will actually be seen or too far down your tweet stream for someone to actually see it. I still believe that email marketing is The. Best. place to build an audience because you have permission to send a message to someone that is almost guaranteed to at least have its headline read.
Of course the rules of the road apply wherever you build an audience, meaning you can't spam or abuse the privilege to talk to them. But all things being equal, owning the channel has some HUGE advantages.
As an infrequent and naive Facebook user, I would not expect that "Liking" a company page meant "Subscribe me to whatever they want to send me."