None of these places Eharmony, Yahoo Personals, Matchmaker, Craigslist, will guarantee a marriage minded person. There are all walks of life and so many different perspectives online, case in point, Yahoo Answers, you get all sorts of advice and answers, some messed up and some worth reading.
Point is, you take chances, especially when finding your companion. If you're going to look for love online, and in this day and age it's very popular, make your point clear. State in your ad you are seriously looking for marriage minded women and when they answer your request, send them several more messages to see just how serious of a person they are about marriage. If that appeals to you then date. Once you meet and ideas change, well then that's entirely up to you now isn't it?
Married after meeting someone on Yahoo Personals 10 yrs ago :)))