Mac Rumors reports that Apple appears to have dropped support for AirPrint in iOS 4.2 on the second-generation iPod touch.

When Apple initially announced the feature on September 15th, the second-generation iPod touch was listed as a compatible device for the service, but as soon as two days later the press release had been modified to note support for only the third- and fourth-generation iPod touch.

  Apple Drops AirPrint Compatibility for Second-Generation iPod Touch