Obviously the attitude of a lot of folks has changed lately. It may be the consensus among people now, that it isn't necessary to give credit. I'm saying it wasn't that way in the past.  I do wonder then, why Renderosity bothers with the vendor credit list they provide for people to check off when uploading an image. Perhaps they want to perpetuate the content business which provides income for the website? Anyway, it's still my opinion that anything not credited is considered created by the poster. I would think you would want to give credit, if for nothing more than to help advertise the person whose products you use. If I use a plugin, I always acknowledge who made it, so that others can take advantage of it as well.  Anyway, I think outside content should be credited. That's my story and I'm sticking to it.