What is a small purchase? a cup of coffee? Where did satoshi specifically say that bitcoin wasn't made to buy coffee but to buy I don't know... Xboxes? where is the cutoff from "this belongs in the blockchain but this doesn't because its too small"??
What does satoshi have to do with this? Do you believe that he was some majestic coder? Because he was not. Bitcoin was never designed for small transactions auch as buying coffe or micro transactions. It is going to be a difficult task to get it to scale like that.