I've previously been skeptical of the idea that OCRing image spams was a worthwhile effort because of the variety of image-obfuscation techniques that spammers had taken to using.
But Nick FitzGerald has recently sent me an example of an image spam that seems to indicate that spammers are concerned about the effectiveness of OCR. Here's the image:
What's striking is that the spammer has used the same content-obscuring tricks that we've seen with text (e.g. Viagra has become Vi@gr@), perhaps out of fear that the OCRing of images is working and revealing the text within the images.
Or perhaps this spammer is just really paranoid.