As a mom of many, my thoughts are that he's simply entering into a new developmental phase and becoming his own person.
He's learning that he can influence his environment, that he can demand and that he can express emotions when he doesn't get what he wants. As a newborn/baby, life is pretty simple: wants are simply mom's milk, naps, and lots of time near people. :) As he grows up and out of babyhood, he's learning that he *wants* a lot of things, and when he doesn't get what he wants, he's learning that he can get mad.
So what is happening is PERFECTLY NORMAL.
You, as the adult, need to help him mature into happy healthy adulthood, so while you want to encourage him to express his needs and wants, you also need to ride that fine line of balance where you *don't* allow him to become the family tyrant. That simply means you provide the boundaries of what is acceptable and what isn't.
For example, in our home, if a toddler pitches a fit, he doesn't get what he was pitching the fit for. I have a 23 month old right now. When he pitches a fit, we all just kind of look at him funny and walk right on by. He's learning that he's welcome to pitch a fit, but that it's NOT going to help him get what he wants...he's just wasting his breath, more or less. We don't give fits ANY attention.
An older toddler (one who can use words and understand a little more) is told that he's welcome to pitch the fit, but that he needs to do it in his room so that he's not hurting the eardrums of the others in the family. Sometimes that means I need to personally put him in his room, if he's already out of control. We're very clear: it is NOT a punishment. He *is* allowed to throw fits. It's okay to be angry. We're simply thinking of the needs of everyone else in the family and having him be angry in private. He's welcome to come out as soon as he feels better. This works really well with older 2's and 3 year olds, and I've yet to have a child after age 3 throw fits.