From the Ray Parker Jr files
A few people I know have mailed me about/linked to articles like this one, which claim that gazonga-ginormifying gum* has become a "big hit" in Japan. I'm going to go on the record and say that I've never heard of it, which leads me to suspect that the whole thing is not quite as big a deal as the BBC believes.
You can look at the company's website here, which mentions a mid-march Health and Beauty Show. (Note that according to this page, the gum went on sale last July.)
I further note that Google News in Japanese doesn't seem to have any stories about the gum, although there are other Health and Beauty Show-related stories about nanocapsules and 15-minute blood analysis by cellphone. Nor does a quick web search reveal much non-commercial buzz about the gum, except for people linking to it going "heh, breast-enhancing gum". And none of my female friends have mentioned it**.
I therefore propose the following explanation: that the gum is probably selling quite well to the usual health-and-beauty-product demographic, but that talented PR people in the Bust-Up booth at the Health and Beauty Show managed to get a few foreign reporters convinced that it was a wild fad sweeping the nation like some voluptuous Mothra. (It certainly wouldn't be the first time journalists had proved willing to believe anything they were told about Japan, especially with this kind of sexualised zing.)
But I must admit, I could be wrong. My Googling skills have proved unimpressive in the past, and I haven't exactly gone out of my way to ask my female friends if they ever chew gum to make their breasts bigger. So I invite my readers, especially Japan-dwelling ones, to share what they know in the comments section.
* I know, I know. I don't normally use the word "gazonga", but I couldn't think of a better word that alliterated with "gum".
** Although, of course, they wouldn't, would they?
butterflyblue:
Actually Matt, we chew that gum all the time while you're not looking. That's why all over Japan, women's breasts are so much bigger this year. Just kidding. I don't know a single person who has mentioned it, or whom I could imagine possibly using it. I'm under the impression that many Japanese women think big breasts are rather tacky. It sounds like an obscure novelty item that just makes a funny news story outside Japan. If Japanese women were so into cleavage, why wouldn't they sell shirts and sweaters here that show some?