SocialMedia.comhas just launched TwitterSparq as a pay-per-performance ad platform that allows you to target keywords and users across Twitter. For the first two weeks all accounts will be free of charge and thereafter costs will be based on a per-tweet basis. Advertisers can bid on placements using the same auction-style format that is used in PPC advertising. According to their site “our Sparqs run on Twitter.com via the PowerTwitter browser plugin, the TwitterFon iPhone client via adwhirl, and several publisher websites, but we are rapidly scaling our distribution.” This suggests that the reach may be somewhat limited at first.

We’ll be anxious to learn more and here stories from early users about how the system is working for them. For instance, getting someone to re-tweet your ad is a somewhat different concept than getting someone to click on an ad. I wonder how that will work.