How is the division made between General and Social?

I’ve often found it difficult to figure out whether a question belongs in General or Social. For example, often I will be eliciting opinions on weighty subjects, with expectations of long, well thought out positions rather than a straw poll of every runny nose with a keyboard and two working fingers. The way General is described makes it sound like it’s restricted to questions with factual, verifiable answers, but Social is clearly not the place for deep discussion, since the description says that humour and off-topic answering is encouraged.

How is the General/Social split supposed to work?