I was screwing around for too long with various installers on my Mac, trying to get the latest available Java runtime working from my terminal.
Finally, some kind soul on StackExchange I think mentioned that if you want to get Java on the command line working, you have to install the JDK package, even if all you need is a JRE. Thanks, Obama!
Anyway, after installing the package from Oracle, now all is well.
$ java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)