The point to be made here is that YouTube is technically also the same service, doesn't matter if you are hosting a website for audio storage, you are a data storage cloud. This is a minor headache for YouTube, and a valuable opportunity for the advertising industry
It's not really the same on a technical level tho, because YouTube destructively modifies your data (re-encoding the video) while filelockers like dropbox allow you to retrieve your original data as-is. Sure they're both examples of "cloud storage", but one actively modifies your data while the other doesn't.
Plus I can't imagine how this would be a "minor headache" for Youtube or even less how it's a "valuable opportunity" for the advertising industry, nobody's going to store files on Youtube because, if nothing else, they'd end up being many many times larger to download than the original file was to begin with.