yes. the 1gb version already in the market for 2 months..
please refer to apple site
http://www.apple.com/ipodnano/

I think the fake ipod nano can be easily identified. coz the click wheel and the screen are different. the fake ipod has a long screen while the original ipod has a wide screen.. the center click wheel of the fake ipod is a play and pause button while the ori one is not.

However for ipod shuffle.. if you look at it from the front view.. you wont know whether is it a fake one or a original.. they look identical.. i seen one before.