Allotting extra time
One should not expect to receive extra time, but I think it's a nice gesture to give a little if the game gets hairy towards the end. Victory is so much more rewarding when you know you beat your opponent while he played his best. :-)
I guess you could argue that it's better not to give more time since your opponent should learn to manage it properly but, the way I see it at least, time is used online mainly as a loose constraint for keeping the pace of the game at a certain speed (brisk, medium, really slow), not as a rigidly strict rule that must be adhered to at all times (tournaments excluded). If a complicated situation unexpectedly arises late in the game, it's appropriate to add some time, as long as it doesn't draw out the game much.
Alex Weldon: The other side of the coin is that time constraints are a strategic consideration, as much a part of the game as anything else. On KGS, my time settings of choice are 15 minutes main time, 20 seconds byo-yomi, 5 byo-yomi periods. Not insanely fast, but pretty fast. If the opponent is playing slower than me, and gets into his byo-yomi time 100 moves into the game, I do not give him extra time, especially if it's a close game. He used his time early in the game, consciously or not, and that extra thinking time will have given him an advantage, all other things being equal. I saved my time for the end, and if I'm losing a bit, and my opponent is low on time, I'll deliberately complicate things (and make my moves fast, so he has less time to think on my moves) to make him suffer for using all his time up in the fuseki. It's part of the game, and my attitude towards all games is that anything part of the game (not metagaming) is fair game to be used to help your chances of winning. If it's a teaching game, of course, that's different, and you shouldn't be using time constraints in the first place.
TJ: Not giving time is fine. Complicating things to burn the clock, doing things you know won't work with proper responses...personally, I think that's not really in the spirit of things outside a blitz game to begin with, and probably carries the possibility of hurting your own go in the long run. I've rarely run into people doing this sort of thing, not being a blitz player, and it always annoys me, and very rarely has had an impact on the outcome of the game.
Gaius: I've recently read a story about a tournament game in which this happened. After one player's main time had depleted, he asked "how long is the byo-yomi time?" Only to find out that the game was supposed to be played with absolute time... His opponent generously gave him 20 seconds, and went on to lose the game.
Jan Stozek?: I had a case on a tournament, when I almost lost a game, unable to manage time properly. My opponent arrived very late, so when he started, he had only about 10 minutes left (+ 10 or 15 seconds canadian byoyomi) out of original 60. He was a very fast player though (and a brave fighter), so we managed to get to late chuban before he almost used his time up. Suddenly I realised, that I am in a serious disadvantage, as I felt forced to respond to his plays as quickly, as he played. Then I slowed down, started to think, more and managed to turn out the board - I killed one of his dragons chasing mine through half of the board. I must say, it was a really interesting experience. :)
- Tomasvdw: Personally, I think your opponent should have forfeited the game at the beginning. Arriving 50 minutes late and still expecting your opponent to play a serious game is not a very polite way to handle the situation especially because, as you say, quick play tends to invite quick answers. It is difficult to take your time when your opponent plays really fast.
damien: I tend to play rather slowly, so my time is often up before my opponents. If an opponent is so kind as to grant me extra time, I immediately do the same for him, as a sort of "thank you" gesture. If I were to grant extra time to someone, I would like for them to do the same for me. Unfortunately, I rarely am given extra time.
This stated, I feel it is bad etiquette and rude to request extra time.