Just because we meet someone online that seems compatible with each other, doesn't always means that it will translate into something substantial. Often I find that we need to ask the person out right there and then, for a drink, a date or just down right dirty fun, if we were to expect anything out of it. Else, with the momentum lost, all will be lost.
Unlike the good old days where msn is still around, we can drop by to say hi whenever we see the person online, because often, when we see another person on msn, it means that the other guy is free. But nowadays with whatsapp or line, it's hard to tell if the person is busy with something or not. True, we can still say hi, but how disappointing it is when the person fails to reply or maybe decided to ignore the message instead. I know I have done that many a times, ignoring messages from online acquaintances.