I've written quite a few of them and there is a trick around people using OCR to get the text. It's commonly known as cross-hatching (yea, just like in 7th grade art class).
Basically instead of "S0m3 73X7" the text would be skewed and on the layer above the text would be lines and quite possibly a gradient to aid in throwing any OCR's off.
Nothing is fool-proof, but you can at least slow the readers down.
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Mr. T!
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