So I was reading the science news over at the BBC when I came across this article:
Although there are still those who argue over the US and “former UK” definitions of figures such as a billion and trillion, according to Michael there is now basic agreement that a trillion is a thousand billion and a billion is a thousand million.
Maybe it’s my American-centric upbringing, but was there really a debate about this? I went and consulted a few dictionaries. Merriam-Webster says:
The “number table” gives the following (American, British, integer) triples: (billion, milliard, 109), (trillion, billion, 1012), and (quintillion, trillion, 1018). Apparently 10n where n = 3 (mod 6) and n > 14 don’t warrant their own name — they can be a “thousand 10n – 3.”
The regional bias is clearer in the American Heritage versus OED. The American Heritage Dictionary puts 1012 first:
1. The cardinal number equal to 1012.
2. Chiefly British The cardinal number equal to 1018.
The OED has its own bias:
The third power of a million; a million billions, i.e. millions of millions. Also, orig. in France and local U.S., a thousand ‘billions’, or 1012 (i.e. the traditional English billion: see BILLION): this sense is now standard in the U.S. and is increasingly common in British usage.
An Ergodic Walk 
Yes, it is your American-centric upbringing. In the rest of the world (not only the UK, and also including non-English speaking countries), we prefer to say that one billion = 10^12. The problem is that you work ” in base 10^3″, whereas we work “in base 10^6”. The same way you say “one hundred thousands”, we say “one thousand millions”.
I’ve heard of the British billion being our trillion, but I always wondered what they called our billion. Now I wonder if anyone there actually uses “milliard”.
The US won this debate long ago. I never heard of the old definition as anything other than a historical curiosity in 22 years living in the UK.