>failing at online dating
I think people fall into the trap of thinking things are too good to be true (so they must not be true). This results in abandoned relationships that would have been better than 99% of those from pre-online-dating times.
This has been true for me, anyway. Every time I've entered the online dating scene, I've invariably realized 3 months later that one or two of the women I turned down for second dates were great matches.