If you only looked at campaign effectiveness in that context you wouldn’t invest in things like Banner ads, certain types of generic keywords, and other ‘upper funnel’ tactics because you’d never see any results. The results would be skewed towards lower funnel tactics like coupons.
Campaign stacking allows you to append the tracking codes into a unique string to understand the progression of events before a purchase occurs. So now you can see as visitors go from an upper funnel keyword like ‘computer’ then to ‘thinkpad’ and then later on type in ‘thinkpad t61’ and then go through an affiliate for a coupon and purchase. In the old way, only the affiliate and the keyword ‘thinkpad t61’ would get credit for the sale. But now we can see the assist that the keywords ‘computer’ and ‘thinkpad’ had in the ultimate sale.
Previous data capture was: thinkpad t61 -> affiliate coupon = sale
Now its: computers -> thinkpad -> thinkpad t61 -> affiliate coupon = sale
Bidding on the keywords like computer now show an ROI as an assist.
The one thing I’d love Omniture to figure out is what to do with the data. Right now I can capture the tracking code string, but parsing through to see patterns is impossible in SiteCatalyst as its capturing everything as a unique string. You have to export into a database or a spreadsheet with macros to make any sense of it. So Omniture if you are listening, please invent a way to see sequences and patterns based on Campaign Stacking. It would save the world.