According to the New York Times, it’s hard to delete your Facebook account.
While the Web site offers users the option to deactivate their accounts, Facebook servers keep copies of the information in those accounts indefinitely. Indeed, many users who have contacted Facebook to request that their accounts be deleted have not succeeded in erasing their records from the network.
Apparently, to successfully delete your account, you have to delete all the information it contains:
Facebook’s Web site does not inform departing users that they must delete information from their account in order to close it fully — meaning that they may unwittingly leave anything from e-mail addresses to credit card numbers sitting on Facebook servers.
Only people who contact Facebook’s customer service department are informed that they must painstakingly delete, line by line, all of the profile information, “wall” messages and group memberships they may have created within Facebook.
Based on what I read here, it seems like the basic conflict is between Web 2.0 principles—you want to keep customer data, because “data is the next Intel inside”—and customer usability. This is a site-wide problem for Facebook; their global settings aren’t comprehensive enough, and too many privacy settings have to be set individually for each app. However, I think Facebook has a good track record of responding to problems noticed by readers, so I wouldn’t be shocked if this issue was dealt with soon.