Since 3rd party cookies are going the way of Friendster, my plans are gonna have to change :-(
I have about 60 domains parked on top of the main domain, and I show different content based on the domain. But I was planning to start diverting at least all mobile users from the parked domain to the main domain, with the theory that a single domain with 15 million monthly pageviews might be worth more to Adsense than 60 domains with the same traffic spread out.
// getCookie() and setCookie() are separate functions I've been using for years)
// on the parked domain
var username = getCookie('username');
// login.js on the main domain
// cookie_name, cookie_value, days before expiration
setCookie('username', username, 365);
But I guess that this isn't going to work, now that 3rd party cookies are being blocked?