Who gets the credit?
Justin Cutroni has a great post on “How Does Google Analytics Track Conversion Referrals?”. One of the key things about this post is that he is able pinpoint exactly what can and cannot be done with utm_nooverride.
This does highlight though the bigger picture issue of allocating marketing spend appropriately. In an e-commerce scenario, where marketers pay for PPC ads, organic SEO and shopping comparison engine listings, the issue is giving proper credit to those channels. By default, GA only gives credit to the last referrer that resulted in a sale. However, it is quite possible and common that shoppers would interact with the site across multiple visits. The first visit may very well have come from an Adwords campaign, but then the shopper decides to do some more research and visits Pricegrabber and then revisits the site. If the transaction occurs then, Pricegrabber would get the credit for the sale and not the Adwords campaign.
Some marketers actually argue that the first referrer should get the credit and not the last one. If the first visit was from an Adwords campaign and the second visit from Google organic, it seems impossible to give credit to the Adwords campaign; even if utm_nooverride were possible to implement for organic listings referrals, the standard Google Analytics code would still ignore it.
The upshot is that quite a few marketers are wondering if they are justified in their PPC spending because GA shows fewer sales attributed to PPC ads. If the marketer then turns down PPC spending, he might find that sales will go down, despite the fact that GA tells him that the ads are not working properly.