The bathroom plaster walls have many hairline cracks. This wouldn't be an issue, except the most recent (and I use that term very generously) coat of paint was a cheap flat finish. That's not good for a humid environment where you might be inclined to wash down the walls every once in a while (aforementioned previous occupant wasn't so inclined if the state of the bathroom is any indication, so perhaps he wasn't concerned with scrubbability)!
Everywhere that the plaster cracked, the moisture worked in under the top paint and opened up a meandering pathway of chipped color. It was an ongoing process, and I continually found little flakes of paint on the floor, on the baseboards, on the towels, etc.
It's all white on white, but on the left side you can really see the cracking paint; the dark shade on the upper right is the beginnings of my skim coatSomething was needed to stabilize and smooth the surface. So my project today was skim-coating. I scraped and sanded everything down a few days ago, and this morning began the slow process of troweling on a thin coat of drywall compound over all the walls. It's setting up as I type, so I'll be back in there this afternoon sanding and touching up. I'm hoping this will work, as Sherwin Williams has a big paint sale this weekend and I've been chomping at the bit to buy and apply my wall color!