Outside of malicious usage, this technique has also been used by VPN providers to support using Video services (Netflix, Prime Video, etc) in other countries. That was certainly the case a few years ago but I am not sure how prevalent that is today.<p>Most video providers block IP ranges that are obviously from data centers, VPN providers, etc. To work around this, many of them would route the traffic for those providers through other VPN customers in the relevant country.<p>Curiously, at least a few years ago, they mostly needed to only route the "control"/API traffic, and it still worked if you pulled the actual video data directly from the normal VPN IP ranges. But that is trivial to fix techncially so I was always surprised that seemed to persist and most VPN providers still have working access to such video providers now.<p>I would be interested to know the state of the art in this battle, but unsurprisingly it's not super commonly written about.
Proxy providers like SmartProxy, Bright Data, and others, offer residential and mobile proxies. This is how they get them (I'm not making any specific claims about who's behind the apps in the article, and each proxy provider makes their own claims, albeit opaque, about the source of their proxies being ethical)