I think a watermark looks good, done tastefully. Not a bright red blob of text over the subject's face. That said, I've never watermarked any of my pictures. None of 'em would be good enough to steal. xD
Generally speaking, I like watermarks because they let me find more pictures done by that person.
facebook // dA
Want to help create a US anime convention map?
COSPLAYS IN PROGRESS
Canterbury (Kuroshitsuji) - 30% - Kuro Gathering
Utatane Piko - default (Vocaloid) - 15% - Ohayocon
Boris (Alice in the Country of Hearts) - 3%
Armin/Jean/Levy (Shingeki no Kyojin) - 0%