What is Buddhism's view on divorce? In some religions, marriage is perceived as eternal and is a bond that can not be broken.

I believe I have read that marriage in Buddhism is not a formal or well-defined institution as it is in Christianity or other religions, but I am not sure.

In Buddhism, is divorce permitted between lay people ? Is it frowned upon ?
It is frowned upon in cultures influenced by Buddhism depending on the situation. If you are abandoning your family because of your sexual desire or craving towards wealth, fame, power of another person, it's frowned upon. If you are getting divorced simply to get away from responsibilities, it's frowned upon. If you are leaving the lay life to become a monk or a hermit, it's accepted. If you want a divorce because you don't get along well with your partner, you are first expected to try to correct yourselves. Be more tolerant of the differences and resolve your problems according to the Dhamma. There's very good advice on how to lead a successful marriage life in the Singalovada sutta.

There's no 'soul-mate' concept among Buddhists as they don't believe in a soul. But the general advice is to stay celibate until you get married and limit yourself only to one partner afterwards.

There's no encouragement to get divorced in Buddhism. You can make a case with the verse in the Dhammapada Balavagga which says: 


  Should a seeker not find a companion who is better or equal, let him
  resolutely pursue a solitary course; there is no fellowship with the
  fool.


But that's for finding friends in general. In case of marriage, it should be applied in the first place, when you are looking for a partner to get married to.