> You should use www because today you have a small web site, and tomorrow you want a big web site. Really big.

Isn't this pre-optimizing? You can use naked domains today and redirect tomorrow when it becomes an issue (IF it's still a technical issue we need to worry about at that time).

301 is built for this.

Or, when you do become big, this becomes a tiny issues.

> Twitter, for instance, which does not use www, had to buy new domain names just for static content.

Do you think Twitter struggled to afford this in any way?

> You may not run into any of these issues today, but as your web site grows, you eventually will.

Again, a big company can easily afford this. Do things that don't scale. Worrying about www should not be your initial concern.