A riskier investment, from the advertiser's point of view, is paying for non-financial actions, like volunteering for a campaign, joining an email list, applying for a job, etc.  When these actions result in offline behavior (i.e. upon "conversion"), it can be financially beneficial to the advertiser: an email list subscriber buys a product, a volunteer sign-up shows up to canvass, a job applicant gets the job, etc.  However, it's often difficult to measure the value of the offline behavior.  More than that, because the online action has to be paired with offline behavior in order to be financially useful, there's always some number of people who don't "convert".  To run a non-financial CPA campaign, the advertiser has to know both the monetary value of the offline action, and the likelihood that an online action will convert.

Somewhere in the world of cost per action advertising is hidden a great opportunity for an enterprising progressive candidate to quietly but very effectively build a solid campaign from the ground up, while helping out progressive blogs.  Besides the obvious (raising money online through CPA), a candidate could do some very interesting things with field using CPA and a fleet of other technologies.  For example, an inventive candidate could develop an mobile GOTV program for harvesting cell phone numbers and addresses from supporters; the campaign would send text messages to encourage those voters to register, and then remind them to vote on election day.

Candidates aren't the only show in town.  Combining CPA with crowdsourcing could provide a compelling way to create a low-cost decentralized newsroom, do legal and other public-interest research, or otherwise gather a wide variety of data quickly and fairly cheaply.  (This is particularly true with VPA, i.e. value per action, advertising.  In this model, ad revenues are split between the publisher, who displays the ad, and the reader, who takes the action.)  Of course, progressive businesses can use CPA to sell things like environmentally-friendly, union-made, or fair-trade products online.

There is an opportunity here for liberal entrepreneurs.  CPA is an exciting technology, but lack of adoption from the blogosphere or from progressive organizations could hamper the degree to which our movement uses it to become more effective.  An enterprising progressive could create a CPA advertising network which makes progressive CPA advertising easier and more effective; such a network could be coupled with tip sheets, resource guides, and consulting services to help progressive organizations and bloggers both figure out how to use CPA.

CPA is about to take a big leap forward.  Last year, Google announced that it would start to incorporate CPA into its AdWords program, and announced the CPA beta test in March.  Turn.com announced a competitor CPA ad network in November.  CPA ads will probably be commonplace in short order.

Progressive bloggers should pay attention to this trend, and take a serious look at their current advertising program.  Bloggers might benefit tremendously from signing up for a CPA ad network.  Bloggers should be aggressive in publishing ads which go well with their content and activities.  Progressive candidates and organizations should begin to purchase CPAs, and think about how CPA could be used to drive their core operations.  There is a serious possibility that CPA could not only make progressive organizations much more efficient, but could also help sustain the progressive blogosphere and help more progressive bloggers earn more money.

If you're a blogger, I'd love to hear your thoughts about whether CPA could be a viable revenue source.  If you're a progressive organization, I'd love to hear your thoughts about the use of CPA.  If you're neither, I'd love to hear whether you think this is all just a scam.