I've abandoned a few accounts, but now, I know how to delete them, and will.
The basic deal is, there's really no way to be completely rid of Facebook. It's just everywhere. But, when you make the effort to delete the account, at least you might have some basis to sue or be in a class action lawsuit against them if it involves some violation of your deleted account.
The URL is hard to fine - it's linked from their help pages.
https://www.facebook.com/help/delete_account There you go.
Enjoy.