If you want to relate this to the web, imagine that you have more traffic than you expected, but can't bring up more capacity right away - if you do your own hosting, this is one of the only drawbacks.

So, you have the choice of throttling traffic, making things worse for everyone but at least everyone gets served, or you traffic shape and most people get full speed but a percentage don't get anything at all due to packet drops.

Looks like Beam decided to traffic shape!