Say what? Scala is statically typed, and does some awesome type inference so that you don't have to declare your type every place you declare a variable. It may look dynamically typed, but its not (http://programming-scala.labs.oreilly.com/ch12.html).
There are numerous holes in the type system. Just browse their bug tracker to see. And several of them are not just "bugs" but deep flaws in the type system.
I think the key thing is that there is no mechanism to be sure that messages you send to actors are immutable. There is a compiler plugin in development to help, though.
So I'm curious, can you point to known problems with Haskell or ML that do not involve using the unsafe features? Scala has problems even without resorting to "unsafe" features like casting or native methods.
GHC 7 recently broken with the traditional ML type checking / inference mechanism because it's not expressive enough for the kind of the code that Haskell wants to support. Noone has this stuff figured out, certainly not ML, Haskell, or Scala. Benjamin C Pierce has even written about how some domains are positively painful w/ strong type systems and how contracts are a more expressive solution.
I'd like to see the ideas behind the Art of the Metaobject Protocol applied to type systems. Allow users to selectively fill those holes that relevant for their domain.
I don't see any mention of a specific safety problems. Plus, I am given to believe that there are actually numerous papers on the extensions involved in the Haskell type system. Consider http://haskell.org/haskellwiki/Simonpj/Talk:OutsideIn
That is the paper I'm referring to. Type safety is an arms race with expressiveness and the paper pretty much says so.
REPLY: You're argument is reductive to the point of being useless - i.e. you could write a type checker for a domain of programs so small as to be comical. type safety and the domain of the provable programs are inextricably intertwined.
Hm... As an early Scala/Akka developer, and contributor I would like to see these issues addressed by the team because I'm seeing a lot of trac jacking going on. This usually only happens when there isn't a response to issues.