Came across a new book that would seem to cover the ground that Elizabeth Scalia already scoped out in her "Strange Gods". This one, also written from a Christian perspective, is called (more felicitously I thought than Scalia's): "iGods".
The author said something I'd seen elsewhere, something perhaps a bit unsatisfying given the somewhat murky division between occasionally and more than occasionally:
Most idols begin as good things...When we shift from thinking about something occasionally (a romantic relationship, a promotion, a possession, our family) to obsessing over it constantly, we are turning an idea into an idol. It becomes the thing we cling to, that gives our life purpose and meaning. Idols are anything we're so attached to that we can't imaging living without... What would we hate to lose and feel lost without? Where do our thoughts wander in our free time?