I am taking a break, started the end of February. Will hit the 900 mile mark in a few days when I get back on the trail. For the most part the numbers I have seen have been low. In the beginning I was almost always alone, even in shelters (which I avoid unless there is bad weather). Two nights ago I shared a shelter with one other guy on a stormy night. The next night, also stormy, we were at capacity (6). In one of the link stories above it shows a picture of a crowded camp sight. I believe I was there that day and it was unusually crowded but for the most part, especially if you stay at camp sights vs shelters, I get a fair amount of "alone" time. Not sure what it looks like behind me with the March and April bubbles.
A gun is really not necessary. Plus where are you going to keep it where is is handy to get too? Keeping it from the environment, dirt and moisture can be an issue. I ran across a hiker carrying a gun. I asked him what caliber it was and why he was carrying it. He said it was a .22 and had it for the bears. I told him a .22 would only piss the bear off. He said the noise could scare off the bear. A .22 is not very loud.