As promised last time, let's begin with the idea underlying Serialino's design.
Simply... we wanted to make everyone able to reproduce an Arduino-compatible platform at a reasonable cost, in a quite easy way thanks to the single-sided design, by focusing the communications with pc only on serial port, but without renouncing to an IC for this goal.
The choice of the IC relies upon the classical Max232.
And indeed the ATMega and Max232 are the core of the platform, the biggest components (in DIP format): as well as the ones requiring the major number of connections.
Here is the reason to center them inside the schematic.