Learning is of course awesome. It's the entire point of life. We are all here to learn.
But, excessively doing things solely for the sake of "learning" is actually doing a disservice to yourself. You should do things with tangible applications to real people besides yourself, too.
There are a lot of preliminary or experimental avenues to explore, but once you find a handful with promise, my advice would be to try to follow those more deeply and apply the principles you learned to something with direct applicability.
What you'll find is that by turning an experiment into a product, you've actually learned a lot more than you ever thought that little idea could yield up. You'll gain not only depth but also breadth as you explore the implications of that product in various fields, gauge peers' reactions to the product and marketing, and attempt to develop your idea into a repeatable, profitable boon.
Tinkering is really important for a lot of reasons, but endless, exclusive tinkering results in a very superficial knowledgebase. I recommend that everyone follow several of their promises tinkers down the rabbit hole and see what comes out of it. I recognize that this takes effort and commitment, but I think you'll often be surprised at the results.
That makes no sense to me. Is there some obligation that all hobbies be useless? One of my hobbies is contributing to open-source software. That's useful, right?
As my fiance is so fond of telling me when I say "I'm off to do some work!" when going to work on my programming side projects (which includes open source development with plans for future closed source commercial projects as well), she replies "Until it makes us any money, it's just a hobby. Have fun."
Ah, I screwed it up :(. I meant to say A => B /= ~A => ~B to convey the fact that if someone says that all useless things are hobbies, then it doesn't follow that things that aren't useless cannot be hobbies, i.e.: that all hobbies must be useless. But as groovy2shoes and MattyDub pointed out, I did it wrongly. Thanks for the kind interpretation pilgrim689 (and indeed, I could have stated that to make the same point), but I was just wrong.
Why do you go on walks? Read fiction books? Hang out with friends? I think one of the ruts a lot of hackers (myself included) can fall into is thinking that everything that they do needs to have a point to it that furthers some long term goal. Somethings can be done just because you want to.
Exactly. And just to expand on this a bit, the process and resulting value of an experience should not be discounted. This is the foci of experiential learning. I can only speak for myself here, but the way I've learned best has always been by getting into something and doing it! Not always successfully, but rarely without gaining some kind of knowledge in the process. Importantly, for me, an important aspect of this has always been because it was "cool" to me. It it weren't...I'd probably lose my focus or quickly get bored.
Learning.