The idea of doing that on-line is superficially appealing (shop for the woman of your dreams!!!), but I rather doubt that I personally could make it work -- I need time to become comfortable around a person; the idea of shopping for wives pretty much trashes that.
You don't shop for a wife on-line but you connect with them. Some people - for various reasons - find it hard/impossible to meet others of the opposite sex. On line singles places let people communicate about preferences and values first. It's not like bangable.com - which, by the way is hysterical. After you send emails back and forth for a while you learn about the other person first. Just like here on FR, after a while you get to know the personalities of the other freepers. You also get to know the ones you absolutely would never want to meet!
The advantage to online dating is that you "meet" a lot more chicks. Meeting more people increases your chances. It's the shotgun approach to dating.