The Yahoo Design Patterns library sure seems to think it is.
According to Yahoo's own definition, "A pattern describes an optimal solution to a common problem within a specific context."
I guess here the "common problem" is, how can you get millions of users to come back to your site every day without having to create any of the content myself? Why, you implement the "vote to promote" pattern of course!!
If Digg's pattern is "vote to promote", what's Facebook's? The "indulge voyeurism" pattern? The "spam your friends" pattern?