That seems to happen a lot. Every time something gets posted it seems to get down. That said, I'm pretty sure it's just one guy managing it all as a side project, so it makes sense that he wouldn't want to pay for an expensive host for all the traffic he gets.
It was intermittently up and down last night (US Central Time) before I posted this.
Evan Czaplicki was actually hired by Prezi to work exclusively on Elm, so the project has industry backing.