For those on dA, just get into the habit of checking the "watermark" feature and unchecking the download feature. For others in general, it is easy to remove watermarks but I know it's harder to remove certain ones than others. Writing your name with is really easy to remove, the beveled ones are harder. Just a tip, when I add watermarks I always put it over a vital part of the picture (so it can't be cropped off) and over something with a complicated pattern or place. That makes using the clone tool difficult and many people will be deterred from doing so, even though it's possible.