Is it fair?

We all do precisely what we want to do at any given time. 

I for one, see it as fair to treat others based on the 'big picture' (taking all things into consideration).  Others might distance themselves and isolate the particular game or the particular moment from everything else and treat fairness as an abstract concept applicable to one task at hand.  To each his/her own.

sftac

I think it is perfectly fair, because they're going to get better and remember to hit their clock more frequently. It's just like a normal blunder in a game, you've got to take advantage of it.

How often does that happen? I wouldn't have thought that often.

It happens quite often, maybe like once every five games. 

Chess is not conducive to fair play...

Ok, this forum is destroyed, here come the trolls. Well, just as well. All of the real forum is over.

See'ya later!

It is most certainly the opponent's problem -- it should be something they learn when they play tournament chess. Nevertheless, I still feel like a jerk sometimes for taking advantage of it, so what I usually do is think comfortably, but eventually move still. Sometimes I tell them, but it really shouldn't be the other player's responsibility. If the result really matters a lot I might use it to the fullest extent possible.

But yes, it is fair if this happens to you, as it is your responsibility to hit the clock. As others have said, the extent to which you take advantage of it is up to you: whatever you feel is sufficiently ethical.

The problem is, it seems like such a punishment for missing such a trivial detail; but then if you hang your queen for just one move you'll probably lose too, no matter how good your position was.