It's interesting how much more positive the reaction overall is to spec-work not in design, like Kaggle's machine-learning competitions. There's some negative sentiment towards Kaggle, but much less, and much of it boils down to, "meh, I don't consider it worth my time, but if others do, that's their decision". I'm guessing it's mostly a question of economics; ML consultants don't feel like spec work threatens to seriously affect their pay, while designers are more worried. Photographers seem to be at the far end, with photography forums full of all sorts of crazed ranting, some even claiming that people who CC-license photos and upload them to Wikimedia Commons are unethical.