innodb_file_format Barracuda
So I'm answering this question almost 4 years late:


InnoDB file formats were conceived at a time when InnoDB was independent of the MySQL Server (for example: MySQL 5.1 could run two different versions of InnoDB).
The reason why you would not want to run Barracuda (in 2012) is that it could reduce flexibility in downgrading MySQL (i.e. after a failed upgrade, you want to move back to a version that can not read a newer format).  i.e. there should be no technical reasons why Antelope is better.
In MySQL 5.7 the innodb_file_format option was deprecated.  Since MySQL and InnoDB are no longer independent, and thus InnoDB can use the MySQL rules of upgrades and what backwards compatibility is required.  No confusing setting required!
In MySQL 5.7, the default switched to Barracuda/DYNAMIC.  Since all currently supported releases of MySQL can read this format, it is safe to move away from Antelope and still offer downgrade.
On a MySQL 5.7 server, Antelope tables will be upgraded to Barracuda/DYNAMIC on the next table rebuild (OPTIMIZE TABLE etc).  That is unless they were specifically created with ROW_FORMAT=oldrowformat.
In MySQL 8.0, the option innodb_file_format is removed.




MySQL 5.7 also introduces the option innodb_default_row_format, which defaults to DYNAMIC.  This addresses the point in your update.