Another personal attack?
Lets see,
I'm supposed to be foaming at the mouth and relying on hyperbole. Now you are questioning why I should have a Facebook account?
Why the ad hominem attack?
Can you not discuss the topic without giving out abuse to people you do not agree with?
Can you explain why I, and others, have the username/password boxes as per my screenshot?
As for how secure your details with them are. Recently some Facebook app writers were caught selling of user details. Going back further, you'll find tales of some T-Mobile staff selling personal details of customers off without management's knowledge.
Do you really trust everyone in Facebook (and their selected partners) who have access to the whole database? It only takes one person getting a wad of cash dangled in front of them and your data will be as safe as a database burned to CD in the hands of a train riding government employee.
If you want to go trusting them with your passwords, thats up to you.
But there is no need to get derogatory about those who are not so trusting as you.