Focus can be thought of in two general ways in photography. There is the idea of focusing our creativity and our energy into making a great photograph and there is the physical act of focusing the camera. Both of these concepts are intimately linked and this article is going to explore just how that relationship works. Specifically I am going to address focus in wildlife and bird photography, but it can be applied to any type of photography.
I cannot count how many times I see a great shot of a bird out on Flickr, and as I am admiring it I then realize that the most critical part of the image is out of focus. In wildlife photography this is generally the eye of the critter. The eye simply must be in focus.  I see focus problems with birds on a stick, birds flying, and birds vocalizing. It is a common mistake that can be easily avoided by knowing where to focus and then concentrating or "focusing" your eye and the focus point on the spot where you want the focus to fall.  Don't be so overjoyed with the subject that you forget your viewer.
Is it about you or the viewer?
As a photographer and an artist, I am constantly in a struggle between shooting a piece for me, or shooting a piece for the viewer or buyer.  In reality, in my case, I am usually shooting for both myself and the end viewer.  Let's be honest, if everyone was shooting for themselves and themselves alone, they wouldn't post it all over social media for likes, faves, thumbs ups or whatever other  type of encouraging gesture is available by your favorite social media outlet.  So we have established that the viewer is the target audience of most of our work, but why do we see so many awesome shots with a focus problem?
Why did you post the out of focus image?
Perhaps this question gets more into the psychological aspects of what it means to be a photographer, but I am going to look at this with logic, reasoning and experience.  It all starts on the day of the shoot.  We spend hours planning our next photo shoot.  We look on the internet at Google and Google Maps results, and pour over page upon page of the ramblings of other photographers and their photographs.  We plan to arrive at our location and spend the entire day shooting.  
The process begins when first, we wake up at 5:00 am, grab a shower, load the gear in the car and speed off down the road. After arriving at the location we quietly move into position, get set up and wait.  We wait for the perfect light, the perfect expression on the animal and the peak of action.  We have built up a fury of expectation that we will get the shot and it will be a good one.  
As we quietly wait in our blind or hidden in the woods, we see a hawk soaring above the meadow just as we had envisioned.  Quickly we raise the camera to our eyes,  line up the hawk in the focus point group and being firing off shots. It all happened so quickly and the thought keeps entering your mind, "Did I get the shot?"  We continue our waiting and it goes on for hours, but the hawk never reappears.  
Later that night, we get home and load our images into our favorite post processing software.  We quickly go through each image and then we find one.  "It isn't too bad. It's in focus", we say to ourselves.  We so desperately want the time and energy we spent on the trip to have meaning and produce a photo that we lie to ourselves.  We tell ourselves it is good enough.  Folks, if you are telling yourself that, then you may never get there! None of us will! There is no "good enough."
 Before you get too upset with what I just said,  I do want to say that everyone out there is at a different part of the learning path including myself and so I don't want to sound like I am preaching here, but there is a point where you must accept that you missed the shot.  You did your best, but it just didn't happen and there is absolutely nothing wrong with that.  However, it is wrong to tell yourself that you nailed it when you really know deep down that you didn't.  I have to be honest with you.  I am a terrible birds in flight photographer.  Once in a while I nail one but there are many times I go home and erase every image I took.  Don't force it.  Learn and keep practicing.  I'd rather post 3 good birds in flight shots a year than 20 bad ones.
Is it Lack of Education?
Another problem with people posting images out of focus might just be lack of education.  Ask yourself what the subject is and how can I best use focus to accentuate the subject.  If it is an animal then compose the shot and get that eye in focus.  If it is a deep scenic then learn to use hyperfocal distance and focus on a foreground object letting depth of field carry the rest of the focus.  Learn your craft and keep at it.
In the end have fun with your photography and stay focused on focus.  Make it part of your routine and it will start to become automatic.  The more automatic it becomes, the more you can concentrate on the peak action and the gesturing of the animal. I also want to say that when I say "in focus" I mean critical focus. I mean at 100% zoom the image is in focus.  Why does this matter?  Because there is so much competition out there, and the expectations have risen dramatically as cameras and monitors improve.  Slight imperfections are only magnified more.  I also want to say that I have been down the road of denial and being satisfied with mediocrity, and I am learning to overcome it and so I thought I would pass along what I am learning.  What will take you from mediocre photographer to a focused photographer?
Below are two critically sharp images.  You should see how many I rejected from each of these shoots.  What if I had focused on the hummers wing?  At that range the depth of field would not extend to the eye.  What if I had focused on the vulture's shoulder?  Again, the eye would be out of focus.  If the head and eye are in focus, the viewer thinks everything is in focus.