> Not sure how a users' union would have much leverage since they don't pay.
Well, advertisers require traffic. If traffic adjacent to Google ads dried up, so would the value proposition of Google's products to its advertising customers. In this way, users collectively could exercise leverage on Google and its advertising clients by boycotting sites/services that serve Google ads (though good luck organizing that).
I think the 'good luck organising that' is the key bit.
The number of people who care enough about privacy to consider joining a union dedicated to protesting Google Ads but not enough to already use ad blockers isn't going to meaningfully affect traffic.
Well, advertisers require traffic. If traffic adjacent to Google ads dried up, so would the value proposition of Google's products to its advertising customers. In this way, users collectively could exercise leverage on Google and its advertising clients by boycotting sites/services that serve Google ads (though good luck organizing that).