Another hangup that arises from too much poetry (besides that Songs with half-assed lyrics hangup) is a blinding hatred for l33t jargon. It's a number, people. What, just because it looks like an "e", that's supposed to be good enough? Fuck that. I like grammar.

But I'm that weird and that awful; when I see this crap I make a big point out of pronouncing it. "So, check out this post. Says that l-three-threet hax-zero-rs get their snax-zero-rs at Bob's."

And yes, I get smacked a lot.

It all depends on the context, really. '0' could be pronounced "zee-roh" or "oh," depending on if it is sung in a radio jingle. For example, Houston residents will remember the phone number for Gallery Furniture, "six-nine-four, five-five-seven-oh" but my phone number in Houston was "nine-three-zero, zero-two-nine-two."

And don't forget that the Artist Formerly Known As A Symbol But Then Changed It Back To Prince was doing this long before the l33t hax0rs -- ie. 1990's and recent script kiddies -- caught on: "I Would Die 4 U" and "Nothing Compares 2 U" (he did write that one!) In this case particularly is pronunciation self-explanatory.

A final case in which not only context, but subject matter knowledge, is important for pronunciation of the number '3' would be the one presented by Tom Lehrer in his work An Evening Wasted With Tom Lehrer, 1959:

I am reminded at this point of a fellow I used to know whose name was Henry, only to give you an idea of what a individualist he was, he spelled it H-E-N-3-R-Y - the three was silent, you see.

In Japanese, far more is possible. Since in Japanese, each digit has at least 2 pronounciations (some have three, and they even often use the English pronounciations), it's possible to make entire sentences out of numbers, especially if you also use syllables that are only similar to the strictly correct pronounciation.

This property is, of course, used extensively in advertising jingles to hammer phone numbers into your brain. In daily life, the number 39 is sometimes used in lieu of arigato since the separate pronounciation of the digits - san kyu - sounds close to the japlish pronounciation of thank you.