If you lube your chain with something wax-like, something sticky, and you regularly overdo it, then this lube will be flung off at the place where the chain changes direction the fastest - which is in the sprocket area. And since you're using something sticky, it will remain there and not drain through the drain port in the bottom of the sprocket area. Mix this with all kinds of road crap and you've got a buildup of thick black mass waiting to happen.
OTOH if you lube with something light and runny, like the stuff that's in a chain oiler, then whatever is flung off the chain into the sprocket area, can just run down the bottom and exit via the drain port. Possibly even taking some road crap with it. And it would be even better if you clean/lube with a solvent such as WD40.
It would be nice if we could have a poll on the lube type and frequency that people use, and the amount of crap buildup in the sprocket area. And the consequences for the slave cylinder. My gut feeling tells me that people who lube their chain a lot (too often), suffer slave cylinder problems more often, due to the crap buildup in the sprocket area.
I don't think there is such a thing as lubing the chain too often. I like that my chains last over 70,000 km and get close to 80,000 km. (Current OEM chain has almost 73,000km/ 45,000 miles.) I'm just going to have to spend a few minutes cleaning out the gunk in the sprocket area a bit more often. (What would be the best cleaning agent? Kerosene?) I am going to make a point of cleaning that area with every oil change for a starter and see how that works.
Some other thoughts:
-I don't consider chain wax a lube. I think it is just for show bikes to stop the appearance of rust on the links.
-I think that almost anything that does a half decent job of lubing the chain will fling a certain amount (and that is why the chains doesn't; need to be "cleaned".). Regardless of how viscous it is I am sure it will combine with the sand from the gravel roads I routinely ride on and build up in the front sprocket area unless you have copious amount of liquid running that will dilute it enough so that it runs. (I have to do an experiment and try combining different viscosities of oil and tranny fluid and even WD40 with sand but I am sure that all of it will combine with sand and cause a buildup. If I have any oil residue on my hands and there is any sand present the sand sticks.) Unless you could protect and constantly bath the chain in oil (like the timing chain) then you need something that will stay on the chain and it will have to have some "stickiness". I would think that even an automatic chain oiler will use an oil that will stick on a certain amount else it would have to use a lot more oil than it does. I don't know about Teflon but can't see it giving the kind of chain life I get using what I currently use.
-I don't believe that "cleaning" the chain does anything useful beyond cosmetic concerns. I haven't cleaned the last 5 or so chains on my Stroms and all have lasted over 70,000km/43,000 miles. None have failed but were replaced at the closest rear tire swap after 70,000 km.