eesh that thing is an eyesore. I found a source for you.
http://jada.ada.org/cgi/content/full/139/11/1457This is of course using fluoride supplements of high dosage, not ~4ppm or whatever as is added to water supplies. Also, it's nearly impossible to pinpoint the efficacy as many of the supplements are still topically applied through chewing, rinsing, etc, and then swallowed.
Even so, why do we medicate everyone's water when the ingestion is only beneficial for kid's developing primary
(actually i believe it has little beneficial effect on primary teeth) teeth?
as someone who tends to hold more conservative values i can't say i disagree with your questioning. as a future dental professional i have to advocate for that which benefits the overall oral health of the community. It still seems like an unnecessary risk to combat a problem that is easily remedied with even half-assed oral hygiene.
even mild cases of dental fluorosis resulting from overdose of fluoride are very rare now, much less the more serious complications from excess fluoride ingestion. and if your last statement was that easy...well, dentists wouldn't exist in the capacity that they do today (even though it really is as simple as maintaining proper oral hygiene).
typically levels achieved are ~1 ppm.