Good thread, I hadn't thought much about the "lube them or leave them" schools of thought on ball joints and other moving parts subjected to a lot of dirt and grit. I've been lubing them, but now I'm leaning toward the Soundguy camp -maybe I'll start using graphite in a spray can. Could be that I've been "killing them with kindness".
For other applications not involving the "grit factor", I just wanted to put in a good word for "penetrating grease", which I had been using on the ball joints and sleeves up til now. It's great stuff and IMHO protects much better than WD-40 for metal-on-metal lubrication. It sprays on thin to get into tight places like a penetrant, then thickens up to act more like a grease. Good stuff. I still use WD-40 for drying out ignitions.
For loosening rusted nuts and bolts and other stuck things, WD-40 used to be my penetrating oil of choice years ago, along with Liquid Wrench, but that was when I was young and even more foolish than I am today. Later, PB Blaster won me over, it really is good. But I think the king of them all for loosening things is this stuff called Aerokroil. Try it if you can find it, I think you'll be amazed. Sure is stinky though.
There's one other thing I might try on the ball joints - molybdenum disulphide spray - it goes on wet, then dries leaving a thin coat of lubricant that wouldn't collect grit the way oil or grease would.