Something that is specially dangerous is mixing laziness and dynamic vars. If you bind a dynamic var to then return a lazy seq, and the dynamic var is used to generate the seq's elements (e.g. `binding` over `map`, and use the bound var inside the map's `fn`), you may get different results depending on when the seq is evaluated (which is not determined)

This made me waste a whole afternoon once. I was even ready to submit a compiler bug!