After writing my initial post on paid search sitelinks, I was contacted by someone who is testing sitelinks in the field for a retail client. This person, while wishing to remain anonymous (I've always wanted to say that), has gone through the interface, what the benefits are and why it's not a perfect system yet.
The Basics
This only works on ads in premium; ads that appear above the natural search results, not alongside them on the left. You can choose up to ten links to appear underneath your main ad - Google will automatically choose four and the settings are applied at campaign level.
The Issues
Since only four links are displayed at one time, you need to find a way to optimize for the best performing links out of the ten you've chosen. Google determines this much like they determine ad rotation - the best CTR wins the game. Even if you want to have all the traffic driving to your biggest money maker, you might be forced to use other links because of a lower CTR. Pants.
Also, these choices are applied at campaign level. So, all the sitelinks will apply to all of the ads eligible in the campaign itself, regardless of ad group. This can result in irrelevant links showing up for your ads.
Presumably, if you're willing to pay top dollar for a premium ad listing (i.e. top position), you'll also have a fancy tracking system in place to track the campaign's effectiveness down to keyword level. Well, scrap it. The sitelink URL usurps the keyword URL - you're no longer tracking at keyword level.
Tomorrow in Paid Search Sitelinks - The Inside Story, Part II, I'll discuss potential workarounds and optimization techniques to the issues mentioned above. Also, we'll look at the benefits of using sitelinks in your paid search account.