Lately Reddit has been showing me posts in subreddits for some of these services. They pitch "passive income" by sharing your connection, an easy way to make a few bucks by renting out your unused capacity. What happens is that you become an endpoint for their shady VPNs. These subreddits are full of people complaining that they're getting hit by abuse complaints from their ISPs. Naturally, these services claim to forbid any nefarious activity, and naturally they don't actually care.