The topic of watermarking your photos or not has been going on forever and is still going strong on forums on the internet. 
Myself I used to do it for years, but then I stopped. For a few of reasons. 

  1. If someone wants to steal my photos, they have and they will, watermarked or not. 
  2. It doesn't look very nice even if the watermark is a nice logo, font or combination. 
  3. For it to be effective, it has to be big and cover a lot of the photo and why then even upload it.

There are a few reasons to keep watermarking, but I decided a few years ago not to use it anymore and I don't think I will change it back.

Anyhow, here's a pretty good video from Jason Lanier regarding this subject.