Ask.fm has grown like wildfire over the last two years, and now claims 180M monthly unique users. It competes to an extent against fellow Q&A sites such as Quora and Yahoo Answers, but its base is more skewed towards teens. The site handles ~20K questions/minute, and its mobile apps have seen 40M+ downloads.
As part of the deal, Ask.fm's founders will be leaving the company, and IAC will be working with New York and Maryland's attorneys general to help Ask.fm "implement a set of best practices focused on increasing the safety of its services." The site has been criticized for failing to do enough to prevent bullying and harassment.