Mac OS X Tiger's Safari updates include a private browsing mode which lets you surf the web without saving the sites you visit in history, cache, or personal information you enter on the pages.
Apple's Safari page reads, "Go ahead and check your bank account and .Mac email at the library or shop for birthday presents on the family Mac.... It's as if you were never there."
Birthday present shopping and email-checking sounds pretty innocent... I mean, what else would one want to turn on private browsing for? In response to that question, a reader of The Unofficial Apple Weblog hacked the Safari file menu to read "Porn mode" instead of "Start Private Browsing." Pretty funny, those Mac users.