There are many different scenarios here, I know! The instance I was referring too, is the one that was happening. I still like to source where I get a photo, gif, or whatever, from anyway unless I take it myself at this point. I mean if you spent the time to search for a photo or something, what is 30 seconds to add a source to that photo? I guess, if they do not ask for credit then it might not matter to them if you do or not. There are many free to use with no credit required, Yes, personally I like to just go ahead and include a source that way there is no questions asked. It is a matter of opinion, that is what it really boils down too.

If you are entering a contest and it requires a photo you took yourself, don't cut up someone else's work and pass it as your own! I mean in life we have our word and our integrity, a few prizes from photo contest here are not worth giving that up, just my opinion though!