While bopping around the net doing costuming research, I came across an old gem courtesy of the BBC: that it was common for young Victorian girls to have waist sizes in inches equal to or smaller than their ages. This myth is usually (though, to the BBC's credit, not in this case) accompanied by an assertion that young Victoriennes achieved these sizes with the aid of rib-breaking, respiratory-distress-inducing, organ-rearranging undergarments. Let's all cross ourselves and be glad that we're forward-thinking and enlightened, unlike those terrible Victorians.
Except that popular 'facts' about the risks and discomforts associated with Victorian corsetry are incredibly exaggerated.
In the first place, it's important to keep in mind that Victorian corsets were sized before their lacing was taken into account. Just because there are extant 16" corsets does not mean that the girls wearing them had 16" waists--they could have increased the size by four inches or more through lacing. Indeed, given that we don't have a bunch of extant outerwear sized for a sixteen inch waist, it's very likely if not certain that that's exactly what they did.
Yes, it's entirely true that there were girls in the Victorian era who went to great lengths, even to the point of harming themselves, to reduce their waist size. We've got people like that now, too. It's just that the Victorians didn't have nearly as sophisticated a construct built up around the relationship between weight, exercise, and diet. "Tightlacing," as it was called, was to the Victorian Era what disordered eating is to ours: a problem? yes. Something that's often written about, as if stern warnings are all it takes to prevent self-harm? Quite. Universal? Not hardly.
Records of the day do indeed indicate that corsets, especially when laced too tightly, could cause short-term health problems, such as indigestion. They were also blamed for pregnancy problems, but it really doesn't take a rocket scientist to work that one out. They did not, however, cause widespread and debilitating breathing problems, rampant fainting, or a rash of broken ribs. "Fainting couch" is a modern term, and the plays and novels from which that part of the myth emerged are no more an accurate representation of Victorian life than soaps and sitcoms are accurate representations of modern life. Victorian women faced a great deal of oppression, but they were not, as a general rule, inclined towards subjecting themselves to crippling pain and debilitating restriction on a daily basis.
The truth about Victorian corsets is that when sized properly, they were actually fairly comfortable (this coming from someone who's actually worn one for a day at a go). Keeping in mind that this is before the invention of the bra, I imagine that abstaining from wearing a corset might have been the uncomfortable thing for many women. While it's pretty much a given that radically altering your shape through external compression is going to be less than comfortable, the practice was both less common and less extreme than we imagine it to be.
Don't trust a story where it's taken as read that women of corset-wearing eras are weak, fainting tight-lacers too vain or foolish to wear clothes that fit them properly. (Yeah, I'm looking right at you, Pirates of the Carribean; where the heck you got off presenting Keira freakin' Knightley as someone improved by tightlacing is beyond me, but it was lazy and gross). I especially don't trust stories where women except the protagonist or love interest are portrayed that way. If the remarkable feature of your leading lady is that she's risen above the icky stain of girliness to attain manly good sense and depth of character, I've got no time for your faux girlpower.
And while we're on the subject of entirely untrue things about Victorians: They may have covered up a lot, but the curve-hugging silhouette of the later part of the Victorian era left very little to the imagination. The notion that they covered piano legs to keep men from getting aroused by them is a total myth, derived from a satirical piece written by a Brit lambasting American puritanism. It predates the Victorian era.