Longer term, who knows - if steemit gets big enough, then it could attract attention.

That is exactly the whole point of the post. Deal with it now, rather than later.

I don't really get this logic. Take pirate bay as an example. It had more than one domain.

Yes, and it made it tougher, a LOT tougher, because of that single reason.

It's a place to start. A really good place to start. Having multiple mirrors has proven to work well. Why do you think that most sites (like any downloadable software, has mirror 1, mirror 2, mirror 3) -- they do that for load reasons, and even DDoS reasons.

More mirrors is more stability. Then after you've done that, you have more obstacles to tackle, but that is the easiest and most frequent method that we can deploy now.