I happen to know some stuff about this, mainly because I have the fetish aswell, but in a smaller degree. Because the ones all of you posted, are indeed terrible and disgusting. I'd rather prefer clean, small ones. The fetish itself is only expanding "things". Some make up ridiculous stories with some girl getting filled up with air. Other draw it, and others actually preform the inflation by sticking a tube into their anus and a (bicycle)pump on the other end. They say feeling the tensity in their stomach turns them on. Quite alot of females (and males:barf:) do it, and upload it on youtube to show how big they can get.
Out of the dozens of ugly, supersized and disgusting pictures, there are only a few actual nice ones. Then again, most of the good ones doesn't have to do anything with inflation(my opinion). :ohdear:
Anywho, I barely see any of this on the internet when you're not paying attention to it. For example, furry sprays you see sometimes in source games. Questions are welcome.