I see it as nothing more than an expression of the transitory and meaningless nature of most online relationships. Facebook is simply afraid of losing user base because the automated tools make it so easy to leave.<p>In Facebook's defense I must say that any web service or startup would probably complain if another service made it easy for users to destroy their account, especially if the content associated with the account was an indexable source of traffic, and destroying the account (unfriending) would possibly hurt other users.
I recall the grassroots "Delete your MySpace Day" from a few years ago. While it is likely that relatively few people actually deleted their accounts, the meme distributed the implicit message that MySpace might not be cool anymore. Since then, we've seen many articles about how it has become an online ghetto of sorts. Although Facebook is clearly more entrenched and better in so many ways than MySpace, it must be scared of such a backlash. Perhaps they are using C&D letters to quell such grassroots uprisings?