If you want to be world champion or mix it up with the legends in Bobby's Room, you need to be a phenomenal player, but being great at poker won't stop you from being broke and miserable. Everyone in poker knows a 'That Guy', a bona fide poker genius who keeps fucking their life up because they care too much about the game. The archetypal example is Stu Ungar; He won three world championships and over $30 million, but died aged 45, penniless and alone in a crappy motel because he just couldn't get his life in order.
Like poker, software is intrinsically meaningful only as an intellectual puzzle. It can be fascinating and beautiful and it can send you mad. Fall into the trap of believing that poker is a worthwhile pursuit of itself and you end up in the trap - living out of your car or on the crappy end of the Vegas strip, some weeks a millionaire, some weeks a bankrupt. You see them come and go, the bright-eyed but slowly dimming college dropouts who could be living the life of Riley if only they knew something outside of poker, if only they stopped trying to beat the hardest games for the sake of it.
Your usefulness as a developer is only indirectly related to your ability to code. There are bona fide geniuses working in poverty and obscurity, there are utterly mediocre programmers doing amazingly useful and important work. Github is overflowing with brilliant, painstaking solutions to problems that just don't matter. Your most important skill as a developer is choosing what to work on. It doesn't matter how lousy a programmer you are, you can still transform an industry by simple merit of being the first person to seriously write software for it. Don't spend good years of your life writing the next big social network or yet another bloody blogging engine. Don't be That Guy.
The fundamental question behind all these arguing is, what can be considered useful? In the other word, what we do, couldn't be considered a waste of life?
Philosophers have been arguing about this for 2000 thousand years. So I doubt there's going to an absolutely correct answer in near future. What I can offer, is just my personal choice.
Whether we like it or not, whatever we do, whatever we've build, good or evil, will vanish sooner or later. The human beings will extinct, the earth will become quite, the sun will extinguish. It's just matter of time. If nothing we do could make any sense in the long term, how can we consider something useful not?
Like any living things on this world, we, humans, are born to have many instincts, like to survive, to reproduce, to play. And when we don't obey these inner demands, we feel unhappy. So we eat, drink, sleep, f, and make money. However, that's because what we do is useful, or important, or has any meaning behind them.
Some people might feel happier when they can attain something that are useful* for others, which usually bring them more money, food, prestige, and many other things. But some might be satisfied enough by resolving some intelligent puzzles. As long as people don't end up in a crappy motel because they couldn't get their life in order, I guess these 2 attitudes towards life are both OK.
The reason why one shouldn't be That Guy is not because spending all your life playing Poker, or doing Maths, or playing Chess (as in the case of Bobby Fischer) just for the sake of it doesn't benefit others, but because when your level of obsession reaches a certain point, the point of diminishing returns, you just get confused -- you can't tell whether you are still getting pleasure doing it anymore. You've been off-balanced with other parts of life for too long that you've lost the ability to approach your passion purely from intellectual curiosity, as you used to.
So the bottom line is, solving intelligent puzzles is fun, as long as you don't abuse it.
Barring a humanity-friendly intelligence explosion event, of course. (I'll leave the Googling to you.)
There is nothing inherently wrong with pursuing something out of pure passion. If we all thought like that, if all of us religiously avoided being "That Guy", the world would be a much less interesting place. Some of the people I admire the most, who's work has inspired and enriched my life have spend all of their lives being "That Guy".
And I want to take the opportunity to say that I think comments like this don't merit negativity. Treat them like you'd treat them in the world: polite comment, move on. It's like walking down the road and there's a purple thistle flower in all its spiny glory. Purple. Pretty. Move on. You don't have to go stamping it out just because there's a social belief that lawns should only have grass.
The situations you cite do not include the potential for noise overwhelming the signal, so they are not analogous.
I know that a downvote can seem like a judgment on the person, but it's more a judgment on the action, and it can be instructive if taken that way.
[Edit: Not that I've been here that long, but that's how I understand the phenomenon.]
I just am compelled to speak up for what I believe to be right. I didn't mean to sound like I was attacking your opinion, so in retrospect, I shouldn't be saying things like "I can say with absolute certainty..." I don't know anything for certain.
I just believe that the world is a nice place when people can simply say nice things to each other every once in awhile.