I've been debating whether to start watermarking some of my images. I've read that there are some on pinterest that take real exception to people doing this, so it might increase the amount of people flagging your pins. There are some real prolific pinners that watermark, and it doesn't seem to hurt them. Yet I know that I'm far less likely to pin an image that has a watermark on it - most of them look like shit or are too large.
I have yet to see anyone watermark a website URL in my niche - instead they are all one lines, like "pinned by BethHotCakes" Obviously this would be a bad route to take. Your account might get banned, so all your watermarked images that are floating around lead back to a dead account. Yet if you include your website address, doesn't that look really spammy?