That's always been possible - you can just enter the network password in Wireshark and watch everybody's traffic on a PSK network. You just have to capture the initial key negotiation traffic for a particular client.

WPA(2) largely just made it more difficult to brute force network passwords (vs WEP) but did nothing for privacy of the users. Unless you're using certificates for authentication, everything you do is visible to anyone else who has the password.

It's a shame, because it would have been very easy to address by just using Diffie Hellman when determining the session key.