It would be like arresting every free man, woman and child in
1790 Philadelphia
1820 Albany, NY
1840 New Orleans
1990 Washington DC
Plus 3/5 of the slaves!
It’s not really a measure, but I remember when Pat Buchanan wanted to build a wall along the US-Mexican border. Some people criticized it by saying, “it would be visible from space.” I though it was a (nearly) perfectly idiotic idea, but I never understood how visibility from space had anything to do with it.
For an odd unit of measure in widespread use, I nominate the KCMIL.
What is a KCMIL? Very simple - it’s 1000 CMILs.
What is a CMIL? It’s a circular MIL.
A mil, as I’m sure everyone knows, is one-thousanth of an inch. A circular mil is an area equal to that of a circle whose diameter is one mil.
KCMILs are used to measure very large wires (that is, wires with very large cross-sectional area). They kick in for wires larger than 4-ought (0000 or 4/0) - one of the few units of measurement that could make a KCMIL look sensible.
A common unit in my field, which, I’m ashamed to admit, I sometimes in actual, peer-reviewed publications, is the kkm.
That’s the kilo-kilometer.
Otherwise known as a million meters.
Now, there is a perfectly good metric prefix for a million: mega, or M. But nobody ever talks about megameters. Mm? Have you ever seen that unit used? So obviously that’s ridiculous.
But kkm is somehow better?
It’s a quandry, I tell you.
Argh! I sometimes use it in publications. Not just see it. Not even just approve of it. I actually use it.
I swear this is true. Visiting the Sears tower about 4 years ago they said the tower has floor space equivalent to X number of football fields…including the end zones! My buddy and I both thought that was ridiculous because it told us nothing about the size. At least square feet would allow me to compare it to my office or house. I HATE the football field as a unit of length or area.
Also, I have a pal that measures distance in softball throws.
What the hell does “Is it bigger than a bread box?” mean, anyway?
“Hm, no. But it’s slightly more girthy than the sound of one hand clapping.”
Around my residence hall at that ultimate west coast nerd academy known as Caltech, the canonical unit of velocity was bushels per fortnight acre.
Or about .00041 mph to you and me.
I’m fascinated. How do you arrive at velocity from bushels (volume or mass?) per fortnight (time) acre (area)? Not that I doubt you did…I just would like to know how.
Two of the more useful units of measure are “Titanics” and “Hoover Dams”.
“Enough cement to build X quantitys of Hoover Dams!”
“Longer than X quantitys of Titanics!”
Good for: costs, volumes, lengths, thickness, weight- you name it.
“Nice is a weapon” - Tony Millionaire
And let’s not forget about the good old RCH 
Units of bushels are volume -> m^3
Units of area -> m^2
Thus units of bushels per fortnight acre is (with some conversion factor which) (m^3)/(s*m^2) = m/s
The way we measure how much data computer storage media can hold is downright bizarre, not least because there are two conflicting systems in use that constantly masquerade as each other.
The engineer’s scale, the one that makes the most sense given the field, is based on powers of 2. It runs like this:
[ul]
[li]kibi- = 2[sup]10[/sup] = 1,024[/li][li]mebi- = 2[sup]20[/sup] = 1,048,576[/li][li]gibi- = 2[sup]30[/sup] = 1,073,741,824[/li][li]tebi- = 2[sup]40[/sup] = 1,099,511,627,776[/li][/ul]And so on, but commonly available disks aren’t that large yet. This makes sense because you can tell at a glance (almost) how much of the medium a given machine word will be able to address. For example, a 32-bit word will be able to address 4 gibibytes; if you need to access any more, you need to work out a paging scheme of some form. (64 bits pushes you out into the multi-exbibyte range, which is technically known as ‘freaking ginormous’. ;))
All that would be well and good if it wasn’t for marketing and all the other non-technical people who came around and mucked things up. The non-technical people imported the unmodified SI prefixes, which are based on powers of 10. They are perfectly logical and rational when measuring how far it is from here to Saturn or how much morphine Courtney Love can shoot up before passing out, but they don’t really help you when looking at disk sizes and making anything less than an order-of-magnitude comparison between models.
The kicker is that the power-of-10 and the power-of-2 units are almost the same, but the power-of-2 units are consistently larger. So marketing can label things in power-of-10 units and sell it to people who naïvely expect power-of-2 units. It’s as if companies were allowed to obfuscate the difference between ounces and grams when selling food, or feet and meters when selling rope.
The final insult in this sordid, geeky tale is that sometimes, power-of-2 and power-of-10 units are mixed in the same freaking number. Specifically, megabyte is also used to mean 1,024,000 bytes: That is, a power-of-10 megabyte of power-of-2 kibibytes. This is how we arrived at the 1.44 megabyte capacity for the 3.5" floppy disk.
There is a measure of perverse genius behind that last coup. And people wonder why programmers hate marketing.
Try Jane’s Fighting Ships. 
Wales. Every day - or every week, or every month, or every year - we lose an area of rainforest the size of Wales. Or twice the size of Wales So we’re told, anyhow: it seems that “the size of Wales” is the official unit for measuring rainforests. How the fuck Wales got in there, or why it’s considered a useful unit of measure I have no idea - how big is fucking Wales anyway? Can it be subdivided further? This park is exactly one milliWales? That one really pisses me off.
I knew what a smoot was. And I’ve never been to Boston.
I thought our family was the only one that ever said this when guessing something.
We aren’t alone!
Back on topic:
Cows are a unofficial unit of measurement when talking about the savagery and effiencient of piranha’s in action.
“These piraha’s can strip an entire cow down to its bones in less than two hours…”
Here in the Netherlands we use Belgium. Since 1 Belgium is 1.4683093507868521103036719765148 Wales (approximately :D), we seem to be losing ca. 0.68105539167486070140937397574566 Belgiums of Amazon rainforest every year.
Interesting – here in the States we don’t use “Wales” as a unit of area – they’d mre likely pick some state of the same size.
When I lived in Utah there was an article complaining about the use of Rhode Island as a unit of measure. Satying that “an area the size of Rghode Island was inundated” confused people out west, who hear “Rhode Island” and think “state”. But Rhode Island, they pointed out, is smaller than a lot of counties out West. You could lose little Rhodie in the mountains of Colorado or Nevada and never miss it. So when folks out West hear these statistics they think that a “real” state has been inundated, and they think the damage is much worse than it really is.
My wife’s dad used to measure drive times by how many cans of beer he would drink along the way. Yes, he was a drunk.
A guest editorial in our local paper was all about how long a local bridge was when compared to vertical structures such as the Eiffel Tower. It’s not a particularly long bridge (1413 feet), but if you rotated it 90 degrees, it would be taller than the Eiffel Tower.
All I can say is, “So What”? A ten mile long highway, if placed vertically, would be taller than the bridge, too.