I used to be more explicit until I read http://inessential.com/2014/05/04/property_declarations

It's hard to find pre-arc docs, but from http://www.uofuiphone.com/iPA/AppleObjective-CManual.pdf

> If you do not use garbage collection, for object properties you must explicitly specify one of
assign, retain or copy—otherwise you will get a compiler warning. (This encourages you to think
about what memory management behavior you want and type it explicitly.)

So, for iOS there was no default.

Anyway, I'm fine with either. Specially since we have lots of properties explicitly declared strong