I'm not sure how Vehicles or Bank Account is going to help describe access modifiers. There's no connection, and will end up confusing the reader. Foo and Bar are used when the focus is not on the semantics but on the syntax of the language.
On the other hand, if you're going to explain concurrency you might use Bank Account as a name, it could help explain things a little better if there's an obvious connection (e.g. transactions between bank accounts needs synchronization, etc..). But for simple examples that just show the syntax of the language, I think foobar is ok. If you know of any concrete examples that are confusing because they use the foobar notation, feel free to list them in a bug report and suggest any improvements you could think of. Here's the link to bugzilla: http://d.puremagic.com/issues/enter_bug.cgi?product=D , select "websites" if it's a language documentation bug or "Phobos" if it's a bug in the library documentation. I care about documentation as much as you do, so I'll definitely look at any bug reports for the docs.
