Audience measurement firm comScore (NSDQ: SCOR) has acquired ad researcher ARSgroup. This is the latest in a growing list of analytics company M&As, as providers look to become a one-stop shop for cross-media data. The amount wasn’t initially disclosed, though comScore said the deal was all in cash. As a number of the leading analytics companies—Nielsen, Omniture (NSDQ: OMTR), Quantcast, to name a few—develop a wider array of research functions and services, the companies are under more and more pressure to keep up. The insatiable desire on the part of marketers and media companies for better ROI through increasingly sophisticated targeting has fueled the recent acquisitions of audience measurement/analytics firms this past year. Meanwhile, the proliferation of companies in the analytics space has also help drive consolidation the last few months.