Requiring an IP address already eliminates cross-network tracking. For example, lots of people browse both on their PC on a cable/fiber connection and on their phone/tablet on 3G, with different IPs. They also often browse from their work network (yet another IP).
Same with User Agent: not useful if you're using Chrome on your laptop and Safari on your phone.
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Requiring an IP address already eliminates cross-network tracking. For example, lots of people browse both on their PC on a cable/fiber connection and on their phone/tablet on 3G, with different IPs. They also often browse from their work network (yet another IP).
Same with User Agent: not useful if you're using Chrome on your laptop and Safari on your phone.