MySql is a joke and always has been. I blame a huge majority of the RDBMS hate on the fact that many peoples only experience with a RDBMS was MySql. The issues are numerous, but two of my personal favorites are silent data truncation and allowing 'indeterminate' results with non-aggregate or non-functionally dependent columns in the select[1]. 5.7.5 finally changes the default behavior of the former.
There would be no data truncation if you enable strict mode (sql_mode = 'STRICT_ALL_TABLES'). Indeterminate results appear only if the column values in a group are different. SQL standart doesn't allow such selects at all (even if the values in the group are the same) so you have to write longer queries.
MySQL is not that bad, it was used in facebook and wikipedia.
Strict should be the default for something that stores your data. The SQL standard does not allow selects like that for a a reason. Indeterminate results are almost always bad for something that stores data. MySql is that bad [1] and was only used by people who knew nothing about databases to question all of the dumb things MySql did. I'm so happy postgresql is finally getting popular.
FB also uses php, so appealing to it being used is no argument.
