Moxie's point is important, but one that is more important is the difference between anonymization and encryption. If your connection is not encrypted, it may be possible to determine who you are, but something being encrypted doesn't by nature mean that the users are unknown.
In this case, they know each other and communicate encrypted. In Tor's onion routing, the server and user don't "know" each other and they communicate via an encrypted channel. Thus, if someone listens to your tor connection, they still can't see your data [and/or guess at your identity].
I don't think it's worth emphasizing the confidentiality aspects of Tor's "link layer" protocol, given that users really shouldn't conceptualize Tor as something which provides confidentiality for their traffic.
In this case, they know each other and communicate encrypted. In Tor's onion routing, the server and user don't "know" each other and they communicate via an encrypted channel. Thus, if someone listens to your tor connection, they still can't see your data [and/or guess at your identity].