Not long ago I was writing a script which, among many other things, needed to set the Publishable property of a category. In the Tridion user interface, a category has a checkbox, large as life, that says "Publishable". How hard could it be, I thought. :-) 

It turns out that when you work with the API (in this case, the core service), it's not called Publishable (or any variation on that), but UseForNavigation. 

I kind of get it. Back when categories first could be published, the focus was on using them to build navigations. There's even a note in the documentation that says "Before SDL Tridion 2009 the behavior was get or set whether the taxonomy can be used for navigation."

Well I suppose every product as complex (and powerful) as Tridion will have it's history and quirks. In fact, it only cost me a few minutes to figure this out, so it's not really a problem. I'm still going to file this post under "gotchas" though!