(no epub though)
I agree that it might be a bit ugly to have your name on it repeated but it is quite "discreet" nonetheless, and unless your name overlaps with a particular perl keyword, it should not impact full text search.
It's a very small price to pay compared to having physical books only, or Adobe DRM :-/
If this is DRM then so is adding my name to digital documents I write in Notepad or Vim as well.
Fortunately it's super easy to unpack a pdf with pdftk or the like then you can delete the text of the watermark with sed or perl if you like then compress again.
I have a script that removes a list of watermarks automatically prior to importing to calibre.
Come to think of it I should propose this as a feature for calibre.
Thanks, chromatic and PragProg.