Exact same question I have here.
Except that I cannot even really think of a situation where you'd like to block, and get away with other strategy. I just never see how this work before. And it sounds problematic. The problem is, if you are blocking by buying it and have some other engine going on, you just add another copper into your deck which is barely better than a curse, wasted your $5 buy which can instead be some other engine card, and also make the rush happen quicker. In my experience, in those games there's no such "block"; it's who executes the rush strategy better.
On the other hand, surely one can block by ignoring the IGG completely (or take one or two when he's in a good mood), by having some trasher available. It can't be 70% of the games though.