[notsuoh]

When the last time _my_ tweet reached millions of users is not the right question. We see that daily tweets go viral and are seen by millions, some things are seen by a billion people (though perhaps not virally in a short period of time). If people are pumping bitcoin with rampant speculation to get other people on the train to increase its value, just a handful need to go viral to increase value, not necessarily yours or mine specifically.

It's like the Birthday Paradox. The chances that someone in a room shares my birthday are small, but the chances that two people in the room share a birthday is large. It just takes a few of the millions of tweets to go viral.

I won't address your second point at length except to say that it's naive to think that with the ease of broadcasting, suddenly the wall is at rebroadcasting, which can be done with no more than a click and is significantly easier than creating the original message.