Robin Sloan writes about stock and flow as "the master metaphor for media today".
Flow is the feed. It's the posts and the tweets. It's the stream of daily and sub-daily updates that remind people that you exist. Stock is the durable stuff. It's the content you produce that's as interesting in two months (or two years?) as it is today. It's what people discover via search. It's what spreads slowly but surely, building fans over time.
Nail on the head. Although I think you can also consider something like "trust" to be stock as well, in which case you can use quality flow to build up stock.
