This is nothing more than site re-targeting / Behavioral Re-targeting or once called Re-messaging. It's happening all the time and many of the fortune 500 companies play in this arena and have been for awhile.
Now.. for a major website provider to say they are the only one to provide this...I guess it's possible they could be the only Industry website providers currently providing the service out of box so there is no need to go with a different provider but it's not the only way you can get it.
I believe you can now run this "re-targeting" piece with Google Ad Sense due to their acquisition of DoubleClick. DoubleClicks DART allows you to tailor message your previous website visitors based on their past interactions on your dealer website. There are a few other companies like Specific Media and FetchBack that provide their own patent technologies for behavioral / site re-targeting.
Being this is a Google/DoubleClick service..I would not see how it would be "exclusive" to this major website provider.
As for the ethics of this..when I first read about it awhile back, I had my own questions on that level but it's not like personal information is being passed. You visit a site, the site/program monitors your behavior on the website to decide if and when you visit another website (that offers ad space within that network) to "re-target" their message to you. I see no harm in that...If I'm going to be advertised to (and that is never going to stop) I would rather be advertised relevant ads to my previous behavior or shopping habits.
Amazon ALWAYS gets me to bite on their "based your on your previous purchase..you might be interested in this book as well" email.
I have in the past and continue to use site re-targeting. I think it's a strong tool with some impressive numbers to back it up. I would NEVER be in Display Advertising without a site re-targeting piece.
Impressive numbers - when "going after the click". (IMO there is much more to Display Advertising than just the click, but that's another topic)
Example: visitor to your website - clicks through to several pages including inventory - customer leaves your site with never converting (form submission/phone call) but gets cookied - customer finds their way onto a webpage/site that is in your publishers ad network of websites - your Display Ad is re-targeting to this customer and the customer takes action by clicking on your ad and is now on your site again. This is a huge WIN and is where the numbers can make a strong statement. I'll keep the percentages broad here but I have seen upwards of 30-50% conversion on re-targeted visitors. Are the number of site re-targeted clicks high?? No..typically only about 10% of your campaign budget will go towards re-targeting but once you average out your campaign and you are buying your impressions right and you have a solid ad network, your cost per lead or cost per action (however you measure) can really make sense.
Like any online marketing there are many factors that go into this. Your website, ad network, your message and your creative (display ad/banner) to name a few.
Mr. Colby, I'm glad you brought this question to the forums. Display Advertising is something that is not talked about on the dealer level of this industry.
Here is a thread Alex Jefferson started a few weeks back that falls under this same topic.
http://forum.dealerrefresh.com/f43/display-advertising-retargeting-276.html
A few resources on Behavioral and Re-Targeting:
DoubleClick.com || Products - DART for Advertisers
What is Retargeting? Learn About Retargeting Here.
Retargeting - Specific Media - Specific Media is an actual vendor that provides Display Behavioral and Re-targeting services.
BT's most overlooked issue - iMediaConnection.com
Four Guidelines for Behavioral Marketing Newbies - ClickZ
MediaPost Publications Specific Media: Display Ads Lift Searches 12/04/2008
Oh too...I have never had nor heard of a complaint from customers. Most people don't even realize it.