Automated Businsess / Bid Rules

[spacewrangler72]

We use Omniture SearchCenter our paid search advertising efforts. I'm interested in learning how others are utilizing business / bid rules for their paid search campaigns. My goal is to make sure I'm using business / bid rules as best as I can to maximize ROI on our search spending.

Our paid search campaign objectives are based on generating online registrations. So we evaluate success and manage the campaigns based on cost-per-registration (CPR). We have begun using business / bid rules that are designed to adjust bids based on CPR targets. An example of this rule is:

Target X - High Volume Keywords ($50 CPR / $25 CPR)

->In this example, the $50 represents the maximum allowed CPR.
->The rule is designed with two "Action Sets" - 1) If CPR is greater than $50, then we have Omniture decrease the bid by 5%. If the action set is not executed it proceeds to action set 2) If CPR is less than $25, then increase the bid by 10%.

The human logic behind this bid rule is that it does two things: 1) recognizes when keywords are exceeding the maximum allowed CPR and automatically lowers bids, in order to lessen the excess spending per registration & 2) recognizes when keywords are generating registrations at a significantly less cost than the maximum allowable CPR and increases bids, in order to try to increase the volume of registrations that are available at a lower CPR. As the bids are increased on these keywords, it is possible that at some point, they may begin to exceed the maximum allowable CPR. When this happens, action set 1 will then lower the bid.

If you think you have some expertise to offer, I'd love to hear from you. Here are some specific questions I have:

1) Does this logic make sense overall? Or is there a better way?
2) We're not sure how to quantify whether the bid rules are achieving the primary objective of maximizing ROI. It's hard to gauge whether we could do better by manually adjusting bids. Any thoughts?