Captchas, at least recaptcha which is the main image selection one, exist to enforce Google's browser monopoly and force tracking on you. You're not proving you're a human, you're being punished for not behaving how google wants. It's vile.
I don't think that's an accurate characterization because the difficulty of the recaptcha is based upon the property its protecting. If it was just about behaving how google wants, then someone who behaved how Google wants shouldn't get tested harder on sketchier sites.
I dunno, I frequently do recaptchas on Firefox on Linux and it hasn't been a problem for me? It does feel like they make me do the image selection more often, but I've never had any problems completing the captchas and it doesn't happen often enough to bother me.
Possible, but I think the more likely explanation is that Firefox users are just higher risk. I don't think the slightly increasesed rare of captchas is going to drive people off of Firefox.
No, but in whatever little bot/scraper blocking work I did, user-agent blocking was an incredibly powerful low-hanging fruit.
For sensitive material, we would often insta-ban anyone who hit us with a 'curl' user-agent and that definitely killed a lot of script-kiddies' dreams right then and there.
Obviously, if you are a determined "hacker" you would get past that and hit the honeypots but simple filters could filter out enough scrapers such that the rest of the attacks could be manually evaluated by humans.
