I highly doubt many people were paying for WinZip or WinRAR, given that they're a running gag in the IT sector (just like paying for Total Commander). But I'd love to see data on it, if anyone has some.
I honestly am very surprised by this. Does WinZip have any other potential revenue source that could explain this, or is it definitely from WinZip the software?
EDIT Joel's post above hints about enterprise licenses. That changes the equation a bit - enterprises have to pay, and it's very easy to get that money from them.
Thanks for that particular link, it highlights possible explanation - "Never subestimate the power of enterprise licenses". So it's entirely possible that almost no user buys it, but they get their money from enterprises. I'd love to see a breakdown if one's available.
Somebody in the thread says he bought it. My experience is that a lot of SMEs and professionals did buy it. The price was so low, and at one point its features were really essential.