Is #screenshotsaturday supposed to be for gamedev, or do other communities use that hashtag for other legitimate uses?
Nobody 'owns' hashtags, anyone else can use them at any time. I guess it takes a teenage brain to equate '#screenshotsaturday' with somewhere to upload your selfies too. No harm done though, 99% of the uploads are gamedev related. I have seen a full on porn gif on there though, and I look at it on my work computer too.
I like the website because it gives me a quick overview of all the uploads, so I can scan for anything that looks interesting. God help you if you actually want to find out more information though. And forget viewing it on a mobile.