The concept is nice, and works well on mobile interfaces where placeholders are often used in replacement of standard labels. You end up providing the user with

The concept is nice, and works well on mobile interfaces where placeholders are often used in replacement of standard labels. You end up providing the user with additional information, considering each field still provides a label even when filled. For desktop interfaces, I like using a combination of standard (btw clickable) form labels, and HTML 5 placeholders. The label's text is very standard: "Name", "Email", "Password"... The placeholder's text is then used as a helper which holds useful but not vital information. For "Name" you can display "Ex: John Smith", for "Email" something like "john@example.com", and for "Password" just a bunch of dots.