If your intent is merely to share your work with the world then watermarking is little more than a way of signing your art. For some, however, it's a business, and the watermark is intended to allow you to see the work, but also serve as a barrier of protection to improper use. The more proprietary the image, the more obtrusive the watermark might be so that removal of the mark may be impossible without also defacing the image behind it.
Unscrupulous people will find ways of making an image their own, including editing the exif data and internal copyright information to remove your information. There are fee services that will embed additional information that can be tracked by their site (there's one such service referenced in the video on how to share your images from the
Scott Kelby's Annual | Worldwide Photo Walk - site is down presently so I can't reference it by name), but it sounds like the protection lasts only as long as your subscription (sounds vaguely like mob protection).
Bottom line, if you don't care then don't bother. For me, it's always been a matter that an artist signs their work - good or bad - and that's the way I look at it.