I too have been rather bemused, trying to make sense of the folder / directory naming of recent months.
The folders were always oddly named, but it wasn't random - from looking at my various iOS devices in the past (of which I currently have three), all of them seemed to be working on some kind of predefined sequence in terms of the folder names served up (in my case) under Win Explorer in Windows 8.1. Each one of these 'folders' was named with an 8 alphanumerical character name, and would contain up to 1000 images, before moving on to the next one.
Then along came iOS 8. First of all, they seemed to be allowing predefined (by iOS) folders to get endlessly bigger than just 1000 pics. At one point I have 3500 in one of the folders. Then, either iOS 8.1 or 8.1.1 (I forget) changed things, so that pictures were contained in an individual folder for each month. On my iPhone 4s and iPad Mini 2, these are still running on a predefined title (i.e. they both use the same folder names compared side by side, so not random). On my iPhone 5c, every time I plug in my phone, the folders are labelled differently, so this is truly random it would seem. I concur with you that countless folders are being created; even if you only take one picture a month for 12 months, you'll see 12 folders for each of those calendar months (I believe).
My 4s, Mini 2 and 5c are all running iOS 8.1.2. I have no idea why the 5c is behaving differently; to summarise all are creating 8 digit named folders for each month of pictures, but only the 5c is doing this randomly every time I unplug and plug it back in to the USB port. As someone else said above, the iPhone uses some kind of light-SQL database to store and dictate all sorts of things, and I think the folders are generated 'virtually' from this, so there must be something weird going on in that DB on my 5c (and prob your device, from what you've described) that probably only Apple can answer.....
I hope in some way that helps, if nothing else to agree you're not the only baffled here! :-)