In non-spatial contexts, when should I use "this" versus "that"?

Historically, "that" was much more common for non-physical referents, except where it was cataphoric, i.e. referred to something which hadn't yet been clarified. So

To be or not to be? That is the question

but

This is the question: to be or not to be.

"This" would be used to emphasise the immediacy of the referent, or where there were two things being distinguished:

I saw somebody rummaging in a rubbish bin. That appalled me.

but

I saw several people smoking, and one person rummaging in a rubbish bin. This appalled me.

("This" is possible in the first case, and in my judgment brings the activity more to the fore).

I think there has been a trend in the last fifty years to use "this" more often than before, particularly in an academic (or academic-sounding) register. So "This is what we find" as opposed to the more informal "That's what we find".