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> advertising, data mining}

Advertising and Facebook-style spyware deployment[0] are behaviors that undermine society, and are only not criminal due to blatant goverment corruption and, if you want to be overly charitable, being too novel for law to have caught up with. They may not be designed for the express purpose of causing harm, but neither are blackhat SEO, or, for example, shoplifting.

Ironically, your original point was a good one; high frequency trading is fairly clearly positive and certainly not inherently negative. (I don't think anyone believes they're making optimal use of their talents for the betterment of humanity or whatever similar goal, but that's a unreasonably high standard when we're also discussing advertisers and SEO.)

0: Which is what people I've talked to use "data mining" to refer to, although I'm not sure if that's what you meant.