Some fairly good advice on technology choices from DHH.
I don't keep up with him in particular or Basecamp in general, but often times their (and his) philosophy rings true. This is definitely one of those times.
My own personal projects focus on nano-scalability, and that's the reason I choose PHP: it scales down to zero when there are no users and can scale up for some time before you run into limits. The former part is really important to me who doesn't have an audience to speak of which would use anything I make. Hence it's important that stuff doesn't take up resources when it doesn't need to.