ha! no shit. after almost two decades of marriage i laugh my ass off at this online dating stuff. what a farce. it's a perfect metaphor for the shallow cesspool our culture has become...
i'm happy for your friends, but as a practical matter they are very likely outliers in the statistical sense.
to put it in the perspective of this forum, all of my VC buddies put online dating plays in the category of domain specific search. that's a fairly sterile way to look at the process of finding a life partner, don't you think?
but beyond that, there is no credible statistical data, i.e. stats not produced by the companies themselves and peer reviewed, that would indicate these services produce anything like a non-niche impact on the occurrence of marriage in the US.
there are however numerous more deliberate commentaries on the topic of technology and its impact on the social fabric of culture. one of my personal favs is "Alone Together" by Sherry Turkle.
The more interesting question in all of this is why exactly online dating functions are even viable. IMHO the fact that people, particularly in the business we are in (i'm assuming you are in the software biz as well) spend so much time chained to a desk that they cannot go out and actually interact physically with other human beings is the point of my original response.
I have several friends who met their significant others online, and are now happily married with children. But you just laugh...?