It's certainly an MO in a number of countries, like Pakistan and Afganistan, against women and, when reported, almost always by male family members.
I have read that forensic investigators tend to find that any attack involving a person's face is usually a sign of intense anger/passion.....and that almost always leads to someone who knows the person very well. Random crimes do not usually target the face of a person. It is literally an attempt to get at the essence or being or soul of the person to attack the face.
The NYTimes reports that the police say it was sulfuric acid.