This journal of interest is in consideration of the recent massive art theft by art4love, as quite a few chaps have suggested that "watermarking everything solves all your problems".
I will answer you my delicious opinion: NO. Watermarks are butt-ugly. Hidden signatures are beautiful.
Even if Art4Love managed to sell anything of mine, the paintings still have my name right on them, hidden between buildings, in the cracks, or as signs.
And to add here's a very inspiring comment by user "pppanties" from Reddit:
WHY IS EVERYBODY RECOMMENDING HIDEOUS WATERMARKS AND DOWN SCALING?
That's like telling us to build shorter skyscrapers after 911