[Haskell-cafe] strictness analysis on algebraic data types

I'm reading the book "Modern Compiler Designhttp://www.cs.vu.nl/~dick/MCD.html", and in the chapter about functional programming it is stated that strictness analysis in the presence of ADTs (aka records) is a very hard problem to tackle. I'm not sure what the current state of art is here (e.g GHC or JHC), and don't understand what the problem is. Does it mean that it's a good idea to carefully consider when to make data constructor arguments (aka fields) strict, since the compiler can't do good strictness analysis when it encounters say a record with many lazy fields?