Nanigans, the Boston-based ad platform and likely the largest user of Facebook’s ad API, announced a huge milestone yesterday: it’s enabled 1 billion conversions via its platform. Conversions include actions like purchases, downloads, sign-ups, etc. Taken together, those are the key metrics for Nanigans, focused as it is on measurable ROI for online advertising.

As the announcement post makes clear, 2012 was a big year for the company:

The 1 billion conversion event milestone represents the business value that large-scale performance advertisers across retail, gaming and additional verticals have achieved by licensing and leveraging Ad Engine. Consisting of customer acquisition and engagement goals such as registrations, app installs and purchases, the milestone follows another year of high growth for Nanigans. In 2012 the company grew revenues by 150%, nearly doubled its customer base, and more than tripled the volume of ad spend managed through its platform.

Glance through some of the case studies that Nanigans publishes and you’ll get a sense for the ultra-competitive world of ROI advertising. Anything that can’t be tied to conversions doesn’t count. That’s in contrast to the fuzzier and more long-term world of brand advertising; Felix Salmon had a great post on the distinction here. Though brand advertising’s future online (particularly on mobile) may be up for debate, Nanigans is showing the potential for ROI advertising in its continued growth.