The Iterator drop method (defined in Iterator.scala) generates nested anonymous classes. When drop is used in a loop, this causes linear traversal to become quadratic, and will also eventually cause a stack overflow if invoked sufficiently many times.

I wrote up a description and analysis of the problem here:
http://erikerlandson.github.io/blog/2014/09/03/matryoshka-class-construction-from-the-scala-iterator-drop-method/

Recommend the implementation be changed from calling 'slice' to something more like:

def drop(n: Int): Iterator[A] = {
var j = 0
while (j < n) {
this.next
j += 1
}
this
}