Recruiting is using big data to uncover potential talent. But right now it's unclear if all the data currently aggregated can predict whether a candidate will be a cultural fit or work out in the long run.
Whether these algorithms work in the long run (where it's defined as the employee remaining employed by the employer for X years), only time will tell and it should be fairly simple to collect the retention data on employees.
When it comes to cultural fit understanding a candidate's personality is important. I suspect many of these algorithms may not be factoring in data around personality and soft skills. The ethical/moral issues aside, it's possible that sentiment analysis on the prospect's social media communication might give an employer a sense over time of a candidate's emotional stability. Or even an analysis of pronoun usage - studies have shown pronoun usage can highlight depression. But is it fair to do this?
Still, if you break down soft skills to key components like effective communication, leadership, conflict style, etc., I have to imagine there are ways to determine it with data. We reveal so much about ourselves - the independent variables are out there.