[jasode]

>Email is run just like this and it has plenty of reach.

The "reach" in gp's context is "audience reach". A measure of "audience size" in a broadcast type of medium. It doesn't mean reach in a technical sense like "reachable ip address or DNS resolution".

Email is more point-to-point and 1-to-1 rather than 1-to-many. Yes, the concept of "mailing lists" could arguably be described as "broadcast" but it requires explicit subscriptions and is not the same "reach" as Twitter tweets acting as global "billboards".

E.g. this HN site often has user-submitted Twitter tweets on the front page. In contrast, it's very rare to have a mailing list mirror post to HN. The reach is not the same. (E.g. last week, the thread on front page about "Adobe removing Pantone colors" was referencing a Twitter post.)

Another example related to HN... the creator of this site, Paul Graham, created a Twitter account in 2010 (https://twitter.com/paulg). It has 1.5 million followers. Clearly, the Twitter platform gives him exposure that his existing email address (and his web blog at http://www.paulgraham.com, and this HN site ycombinator.com) -- does not.