Interesting article.
It has always been tough to have a profession that is so 'fun' that people are willing to do it for free. Sports, photography, writing, music.. these are all things people do in their spare time as hobbies. It's not too surprising you'll find people willing to do these things for free. When you finally get tired of doing it for free, it's pretty hard to convince everyone they should pay - especially when they are tons of other people still eagerly and happily doing it for free.
indeed but in our case, photographers, lets say musicians/writers as well we all need to start somewhere so we do some work for free believing it will turn into something after, yes it might never happen but if it is taking too long perhaps it is better to move on and let other do the job for free until they fell sick of it as well
summing up we need to try/be relevant and show that our work will make a difference and that an extra expense will be more rewarding for them in the future than having a dude here and there without knowing what will happen next, so free for a short period of time is almost impossible to run away from these days (I see it as part of the process) unless you have a bunch of very good influential friends or insanely lucky to find a person willing to pay you as you deserve from scratch instead of a beer or two!