Things went a-flutter starting on Thursday afternoon when Mac users began noticing their /Users and /Users/Shared folders went into hiding. Initially attributed to the OS X 10.9.3 update, this was actually the result of the iTunes 11.2 update, and only if you had Find My Mac enabled.
Speculation went wild, with many (including Apple Support reps) presuming that this was intentional on Apple's part and now policy.
Apple ended that speculation late last night with the release of iTunes 11.2.1 (also available via Software Update). Install this and you can literally watch your /Users folder re-appear during the installation process. No reboot required.
Thanks, Apple, for the quick fix. Next time a little, "we're working on it" note during the day would have ended a lot of unnecessary concern. But hey, all's well that ends well.