Encryption is key to online safety
It is important, I think, to understand that you should never give a username and password to a web site that has an "http" address, only to "https" addresses. A connection through Tor can be encrypted end-to-end -- but only if one is communicating with a secure protocol -- https: or encrypted chat both would be examples of this.
We are very careful, usually, to only put a credit card into a web page that has a "lock" symbol in the corner of the browser window. Everyone should be equally careful never to give a username and password to a page that is not "locked" -- not secure.
You should at the least use different passwords for insecure accounts, like those at theregister.co.uk, which require you to give a username/password on an unencrypted link. But even this can open you up to people posting things you wouldn't wish to have said in your name.
It is only through understanding our security online -- through understanding tools such as Tor, and what https: means, and what a phishing attack is, and so on, that we can manage our risks online.
The last node through which traffic passes in the Tor network does not in fact need to pass data to the destination unencrypted -- if the origin and destination are using a protocol that supports encryption.
You wouldn't say that the people who make your backup software are at fault if they don't force you to back up your files regularly. We, like the backup software creator, warn people in our documentation that the protection of Tor is not foolproof without educated and disciplined use. And like backup software, if you don't use it right, it can do nothing to change what has already occurred.
We have advised, and continue to advise users of the Tor network to use encryption end-to-end whenever it is prudent and/or possible. But those end-to-end encrypted products (https, encrypted versions of email and chat) are available to the users in many forms -- it would not be proper for us to dictate what people should use, but only encourage them to take precautions.
Development Director, The Tor Project