Few marketers these days want to start a campaign without a good idea of what return-on-investment they can expect. That applies as much to social media as to any other marketing channel.

So its good to see the market leader Facebook teaming up with Nielsen, the market research company, to provide the kind of measurability that businesses need. The project, called Nielsen BrandLift, uses opt-in polls to measure consumer attitudes and purchase intent from display advertising that has appeared on the site.

The idea is that Nielsen will carry out regular surveys with the site’s advertisers, and these will appear on Facebook’s homepage in the same space where people see sponsored messages today. “Together we will be able to provide the missing elements to clients seeking better understanding of how Web content and online advertising affect consumer behavior,” says John Burbank, CEO of Nielsen’s online division.

Nielsen BrandLift will launch in the US with select test partners this week and roll out to all Facebook advertisers in the coming months. More details here.