A recurring theme in our work with clients is to cast the analytic net across their web presences, not just their web sites. For example, let’s say you’re a retailer and you run a “discounted shipping” promotion, with different levels. The campaign for this should be evaluated not just in terms of conversion on your web site, but in terms of how different levels and creative versions performed in terms of attracting, engaging, and converting customers in all the places you published them — display ads, SEM units, emails, your site itself, affiliates’ sites, etc.
Implementing a test strategy like this has been hard to date, because you may not control all of the different properties involved in the campaign; even if you do, each channel may have its own testing tool; and, even if you’ve consolidated things somewhat, the tagging job is still a bear.
Read more: http://www.octavianworld.org/octavianworld/2009/07/testing-across-your-web-presence-a-conversation-with-sitespects-eric-hansen.html#sthash.Jt8wNHcM.dpbs