[dingaling]

> It's extra effort for them for nearly zero marginal gain.

I wouldn't say it's nearly-zero gain; by applying a tiny sed expression they obtain a basically unblockable e-mail address.

It's easy to blacklist [e-mail] but very few people would be willing / able to blacklist their top-level [e-mail]. So the spam keeps coming.

Spammers are annoying but the progammers behind them are smart.