[KillerRabbitt]

While this may evade simple scraping bots, it's easy enough to render the page then use some type of character recognition to get the content.

[nickreese]

I don't disagree. But the bot / tool rendering it would need to know to look for it.

You could even pass around "not so hidden" messages with it. Tell your friends, add this CSS class to the body to see the message.

Bulletproof, not at all. Just pointing out a clever use.

[matte_black]

It’s fairly trivial to quickly animate each letter or stroke to flicker at a random high speed interval so anytime a render captures a screenshot you get garbled incomprehensible text.