I can hardly improve on the article in Wikipedia. You can get it at:

http://en.wikipedia.org/wiki/Long_and_short_scales

It is well worth a read apart from covering this question.

Regarding You asking "among scientists".

What makes You think that this has ever been a problem

for scientists?

Scientists are used to make use of math, if numbers become

"unpleasant" or "lengthy" they use exponentials or they use 

prefixes like Mega-,. Giga,-, Tera- and so on.

They dont ever "respect" MKSA  or other conventions, if

only the numbers are readable. Eg all thermodynamic tables 

still are in calories, all calculation is done with calories,

if sombody asks for, the end result is given in Joules.

Surface tension is all cgs (Poises), and IR is in "wavenumbers"

(a frequency measure), this is number of wavelenghts in one cm.

All this was developed/chosen in order to get reasonable numbers

to write, read and tell.

Believe me, scientists leave Billions to accountants and bankers.

If You read something from scientits on money, like cost for a LHC,

You will read kEu. MEu or GEu.

Georg

There are three things I learned at school that are no longer so, and that makes me feel rather old.

Everest was 29,002 feet high, and it grew 27 feet on the Chinese side, while I only grew 5 foot ten inches.

A billion was a million million, and because Yanks count on their fingers, now it is only a thousand million.

An inch was 2.5402 and a bit centimetres, and now it  has legally shrunk to exactly 2.54 cm to make the French less confused.

To go with the Mars lander getting lost between metres and feet, I did hear of the Shuttle mission which was going to use a laser reflector to measure the height of an observatory in Hawaii. Every time they tried to align the Shuttle, it turned upside down. Apparently somebody had programmed it with the information that the mountain was around 5000 km high, instead of 5000 metres.

It is interesting to read the other replys and the Wikipedia article referred to by Jon in the first reply. Despite having gone to primary school in Australia after the 1974 change over by the UK, I learnt that a billion was a million million.

Now that I work as a mathematician, I still follow the long scale rule for naming numbers, i.e.:

1 = One

10 = Ten

100 = Hundred (Tens of Tens)

1,000 = One Thousand (Tens of Hundreds)

10,000 = Ten Thousand

100,000 = Hundred Thousand

1,000,000 = Million

10,000,000 = Ten Million

100,000,000 = Hundred Million

1,000,000,000 = Thousand Million (Milliard or "US" Billion)

10,000,000,000 = Ten Thousand Million

100,000,000,000 = Hundred Thousand Million

1,000,000,000,000 =  Billion (Million Millions or "UK" Billion)

Of couse, as a scientist, I use the standard SI measurements (metres, grams, etc.) and so when writing large numbers I use scientific notation (e.g. 10^12) or standard prefixes (e,g. Kilo, Mega, Giga, Tera) and avoid (where possible) referring to billion, trillion, quadrillion etc. as the ambiguity of the number names may lead others to misinterpret my statements. When others use number names like billion without also providing the number in scientific notation, I immediate ask for a clarification of whether they mean 10^9 or 10^12.

I also do a fair amount of work with permutations of sporting team player line ups and so I am aware that 11! is approximately 40 million and 15! is approximately 1.31 x 10^12. When I present these figures I am very careful not to say 1.31 billion, but rather "1.31 million million" or "1.31 by 10^12" to ensure my audience is aware of the true scale of the numbers.

With regards to the Mars mission, I like to use that as an example to my students of how "trusting the computer output" can lead to disaster if you don't have an estimate of the correct answer and the correct order of magnitude, especially when working with very large numbers.