For me, I learn from others and reinforce what I've learnt by sharing with others. In retrospect, it doesn't really matter whether what I had formal training per say ... for instance I went for a 3-day Photoshop Workshop a year ago and it cost hundreds but strangely, the Photoshop actions which I am using now are largely learnt from trial and error and from my peers ...
In short, you can learn for free although I know some will feel otherwise.
1 There is absolutely no doubt that one can learn A LOT without any "formal" teaching, either in photography schools, or through seminars, workshops.
Great photographers who had done well are too many to number!
2 Nonetheless, I wonder how many amongst us have the inherent talent and work attitude to be self taught. For some who have given their opinions so far, how many are actually "rounded" in their photography "repertoire"? I put myself in the same list. Example, my "forte", if there is such a term I can apply to myself, is black & white people photography in the traditional way. And even so, a very narrow form of B&W people photography. I do not even know how to use strobes nor even the most elementary of B&W digital processing. I don't even know how to shoot street people photo properly!
If I am an example of the average photog, I think we tend to stick to the genre of photography we like to do, and the other wide world of photography remained little known to us. So, do I know photography? Or just only the little I know (and even so, so little!)
3 I think that for most of us, a concentrated week of "focussed" photography with likeminded people can yield results that may take a long time to acquire. A lot also depends on the instructors. Chjose the teachers well. Not all great photogs are good teachers! My first photography workshop in Singapore was plainly a waste of time as far as learning was concern. Nonetheless, it did me get me started.
4 Having written thus far, I need to clarify. My comments are meant for fairly serious people who want to take their photography a little "further". For those who are contented to make some nice snapshots every now and then, then I think very basic knowledge is probably adequate. There is a reason why people flocked to pay hundreds of hard-earned money just to spend a few days photographying and learning from photog "giants/teachers". Somethings are just difficult to learn without some guidance, unless of course inherent genius is waiting to break out!
I began photography by trial and error, and gathered lots of comments for my pictures. thats where i started improving as comments were used to point out potential mistakes.
now that my photography has reached a 'certain' level, i actually see the benefits of looking for some sifu or photography courses to further my skills, as surrounding friends are no longer able to point out the obvious...
I learned the basics from reading magazines and books. Then applying what I read.
Took some classes when I thought I already reached the limit of what self-training can do for my technique.
Have to couple self-learning and formal classes with practice of course.
No use if you don't go out and shoot.