It's the same thing as writing tickling fiction/stories, except in this, you have two active people playing roles and there is an active element to it.
As for the people bad mouthing, lets discuss:
First and foremost, I certainly hope none of you have had a long distance relationship. When you have two perfectly normal people, with normal (maybe even heightened) sexual needs, a form of cybertickling can act as stimulating play, can fulfill a need, and provides them the ability to get off without, you know, cheating on their significant other.
Second, while it is true that most people will simply make HAHA's and 'seal noises', it is also true that some people take the play and turn it into a psychological indepth writing exercise. While bad to mediocre cybertickling can be horrible to see and disgustingly weak to read, if you have two people who are capable of writing, then you can come out with something very enjoyable. And given some of the responders in this thread, who apparently take a very literary/creative writing mode with their 'tickling fiction', I find their dismissal to be troubling. Because the reality is simple; your tickling stories are in the same boat as that play aspect you just decried. So either you are hypocritical, or you are elitist. And, to be frank, there are no Herman Melville's or Chuck Palahniuk's or Cormac McCarthy's of tickling fiction.
As for the waste of time slam, well, time is a relative commodity. I'm the first guy to be extremely judgmental of others, but the fact remains, if you read tickling fiction at all and get off on it, or enjoy it, then busting on cybertickling is laughable. I don't see how it is any more a waste of time in the true sense than a clip, a picture, a piece of artwork; in all those cases, the person viewing the piece is not necessarily doing any tickling themselves. Those things, by this opinion, are complete wastes of time. So, here's to you not looking at any of those things, because if you do, then you are a hypocrite of the highest order.