My friends and I have been raising this same question this spring. Many of us noticed the same phenomenon. Here are some thoughts:
The weather was hot and dry here last summer. Drought can destroy azalea flower buds.
Was the weather especially cold this past winter where you live? This is another condition responsible for killing azalea flower buds.
Conversely, lack of cold weather can sometimes result in a plant's not blooming.
Were there any unseasonably warm periods in the fall or spring? Sometimes, azaleas are tricked into blooming during these periods (so-called "bud blast"). After such premature blooming, those azalea flower buds are lost to you for the next blooming season.
My only guess about mine is the lack of water. Maybe the two that bloomed got more water.

I had the same thoughts regarding temperatures up & down all winter (and spring!). But it seems everyone else in my neighborhood has bloomed.

Perhaps water was the issue, as I didn't water them hardly at all. I went with "survival of the fittest" for anything that was established (had too many new shrubs that had to be watered). I can't imagine most of my neighbor's actually caring enough to water theirs, but maybe they were doing midnight lawn watering so their azaleas got something out of it. Mine are under a small area of tall pines and a dogwood, so there was fierce competition down at that end of the yard. Maybe I'll try to do a little more supplemental watering this year and see if that makes an impact.

Thanks.

jmz, they may have been zapped in some of the late cold weather we had. I think one day in early March the temps went down to 26 or so. Since azaleas set their buds in the previous summer/fall and they start to come out in spring, they are susceptible to frost kill.

I had that happen on a few of my azaleas. They lost about 20-30% of their buds. I'm sure it was from the cold, because it seems the top branches did not bloom, while the under branches did (they were slightly protected apparently).

Since I had to prune anyway, I cut off some of the older non-blooming branches to better show the blooming ones.

If you look closely, you should see the 'frozen' buds. They will be brown and crumble if you touch them.

Buford, I'll check them tonight when I get home.

Danielle, I hear ya! I can't bring myself to kill anything off either. Part of me knows it's wrong and I should just put a plant out of its misery, but I just can't do it. :-) You should see the pathetic wax myrtle I have that is dieing a slow, painful death.

Ever hear of plants, especially Azaleas, taking time out and going on vacation?
Some of them do, apparently. I have several hundred plants and at times, an entire area will not set flower buds and that may persist for several years.
Plants bloom best when under a certain amount of stress. Survival instincts prompt them to flower and produce seed(assuming they aren't sterile varieties).
Some gardeners fertilize their Azaleas annually with a formulation especially for Azaleas and Rhododendrons, but I haven't found that necessary for mine.
Rb

DON'T fertilize azaleas until after they bloom. Or prune them. Do both AFTER the bloom. I learned that the hard way!