Are web marketers expected to only own 1 adsense account even if they manage different sites?
"We'd like to remind you that once you've been approved for AdSense, you can place the code from your account on any page that complies with our program policies. Simply generate new code and paste it onto your site -- we don't need to update your account, so there's no need to contact us about your new site (although we appreciate the thought!). Even if your sites relate to completely different topics, our system will display appropriate ads for each site. This is because your ad targeting is based on the content of your pages, rather than set within your account. In addition, please keep in mind that publishers may only maintain one account per payee name, so there's no need for you to submit a new application.
If you run multiple websites, you may wish to view separate reports for each domain. Simply create a URL channel for each one. You won't need to modify your code in any way, and your URL channels will begin tracking data almost immediately. If you need to send these reports to other people who manage your site with you, you can set up emailable reports.
But what if you've sold the website you applied to AdSense, and now you run another one? We don't need to update your account information in any way. Just remove your ad code from the old site, paste new code onto your current site, and our system will automatically take care of the rest.
Finally, we'd like to note that we do constantly review sites displaying Google ads to make sure that they're complying with the AdSense program policies. If we find that a site isn't compliant with our policies, we'll contact the publisher whose ad code appears on the site to address the situation. If you're concerned about others placing your ad code on non-policy compliant pages, we recommend using our Allowed Sites feature.
Posted by Arlene Lee - AdSense Publisher Support"