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.

[1] http://grimoire.ca/mysql/choose-something-else