Introduction

Online Dating sites/applications can offer 2 main proposals:
* fun dating, for flirting, for entertainment purposes, for instant gratification; mostly for persons up to 25 years old.
* serious dating, for long term mating with commitment, for marriage with low divorce rates; mostly for persons over 26 years old.

Online Dating Sites/applications can be classified as:
1.0: First Generation "Browsing/Searching Options, Powerful Searching Engines" 1.5: Hybrid; "Unidirectional Recommendation Engines"
2.0: Second Generation "Matching based on Self-Reported Data by personal preferences & likes and dislikes Bidirectional Recommendation Engines" and "Behavioural Bidirectional Recommendation Engines"
3.0: Third Generation "Compatibility Matching Algorithms" e.g. eHarmony, uses a normative version of the Big5 to assess personality and Dyadic Adjustment Scale to calculate compatibility. The U.S. site is different from the UK site, Australian site, Canadian site, etc.

Online Dating had evolved: from "Browsing/Searching Options"to "Recommendation Engines" and now Online Dating is evolving from "Recommendation Engines"to "Compatibility Matching Algorithms"

Experience had shown serious daters never use social networking sites/applications for dating purposes and Online daters belong to 3, 4, 5 or 6 online dating sites at the same time.

There is a range convergence phenomenon between the 3 mains tools online dating sites can offer: searching by your own, Bidirectional Recommendation Engines and Compatibility Matching Methods. Any member receives on average 3 to 4 prospective mates as selected / recommended / compatible for dating purposes per 1,000 (one thousand) members screened in the database.They all 3 are performing the same for serious daters, with a high percentage of false positives, like gun machines shooting flowers.

That range convergence phenomenon is what I had called "the online dating sound barrier", in 2003, when I had discovered than problem, 7 long years ago.