I personally find this offer very interesting. Well, not so much the offer itself, but the manner in which to get it. This thread at FW points out that for the Citi Business card, you can get an extra 5000 bonus Thank You points (for a total of 15000) when you signup if you pretend you don’t really want the card at first. As the poster states:

went to apply for citi business (the one with 10000 bonus) hit back button on my browser, and got a popup offering another 5000 if i don’t back out and go apply, as in 15000 total bonus points to sign up just because i almost didn’t

More accurately, if you apply on Citi’s web site itself (http://www.citicards.com), click on the Small Business Credit Cards link, then click the “Apply Now” button for the CitiBusiness Card with ThankYou Network, it will create another window with the application. If you then close that window, another popup will appear, offering you another 5000 points for completing the application. Such is the world of marketing that we live in today.

On a side note, when I first tried to test this, I was using Firefox with my pop up blocker automatically turned on, so the popup didn’t show. You’ll need to disable any popup blockers you have in order to see this offer.